1 Introduction
In alumina production process will produce a lot of waste red mud, red mud as a red remaining after the industrial extraction of aluminum from alumina aluminum, the aqueous strong base powder, high solids sludge waste. The composition of red mud is complex, containing alkali and a small amount of radioactive materials. The percentage of main chemical components is shown in the table below. The red mud is too fine. At present, most of the domestic red mud yards are stacked in the wet storage method and dehydrated for long-term storage. Water infiltrates underground pollution of groundwater. The latter is easy to cause dust to fly after being stacked and dried for a long time, which seriously pollutes the environment and endangers people's health.
ingredient | TFe | AL2O3 | SiO2 | Na2O | CaO |
content | 28 | 17.32 | 16.8 | 5.5 | 3.2 |
ingredient | FeO | K2O | MgO | S | P |
content | 0.16 | 0.29 | 0.16 | 0.16 | 0.11 |
On the one hand, red mud is industrial waste that causes environmental pollution, and on the other hand, it has its resources. By red mud through laboratory experiments show that can be recovered from the red mud of valuable metals such as Ca, Te, Ti and so on. Based on the principle of reducing the amount and harm of solid waste, fully utilizing solid waste and conducting harmless disposal, the development and utilization of red mud can effectively promote environmental cleanliness, energy conservation and emission reduction, and the development of circular economy.
2 Development of high magnetic dressing iron extraction technology
The iron in the red mud is basically in the form of Fe2O3, and the general content is 10%-45%. The iron powder extracted from the red mud is directly used as a raw material for iron making, and the iron content is lower. In some countries, the red mud is pre-matched and then put into a boiling furnace, and the temperature is reduced at 700-800 degrees Celsius to convert the ferric oxide in the red mud into triiron tetroxide. After reduction, it is cooled and pulverized and then sorted by wet or dry magnetic separator to obtain 62.81% magnetic product containing iron. The iron recovery rate is 83-93%, which is a high-grade iron-making concentrate. . The former Soviet Union used the tandem rotary kiln method to refine pig iron from red mud. However, China's Pingguo aluminum directly used the high-gradient magnetic separator to fully recover the iron semi-industrial experiment. The high-gradient strong magnetic mineral sorting technology was used, and after several indoor small-scale tests, the experience and method of extracting and recovering iron from red mud were obtained. In the flat oxygen plant, an industrial test for extracting iron from red mud was carried out. The concentration, grain size and iron grade of the red mud slurry were studied and tested in the process, and some progress was made.
Analysis of the main components and content of alumina red mud:
Iron is the main component in red mud and exists in the form of Fe2O3. The main components are: TFe 20%-30%; Al2O3 12%-19%; SiO2 15%-25%; Na2O 5%-15%; CaO 3.1 % - 4.1%, of which valuable metals have a high recovery value.
Alumina red mud fraction composition and content analysis:
The fineness and size of the residual tailings slurry produced in the alumina production process depend on the fineness of the bauxite ore. The fineness of the tailings ore slurry directly affects the red mud process, and the iron concentrate grade Have a direct impact. The following analysis and research on the ore slurry size of tailings at different stages, the optimization and improvement of the beneficiation process are carried out, as shown in the following table:
Mineral sample | granularity /mesh | quality /g | Mass ratio /% | grade /% | Remarks |
1# tailings sample | +80 —80+120 —120+200 —200 total | 49.5 34.2 39.7 726.77 850.17 | 5.82 4.02 4.67 85.49 100 | 32.86 33.95 30.21 21.75 23.28 | (tailing concentration 42% -325 items accounted for 50%) |
2# tailings sample | +80 —80+120 —120+120 ——200 total | 150.7 33.3 35.5 481 700.5 | 21.51 4.75 5.07 68.67 100 | 36.37 35.16 30.01 22.57 26.51 | (tailing concentration 43.75% -325 items accounted for 50%) |
After a rough analysis of the ore slurry size of the tailings: the grain size distribution is about 75% for 200 mesh; about 80% for -80+200 mesh; about 15% for +80 mesh; the maximum particle diameter is less than 1 mm.
A number of tests were carried out on the fractional composition of the ore slurry of the tailings. The 325 mesh grade accounted for more than 80% of the total, and the red mud fraction composition had higher muddy content. After the classification and fine grinding, the red mud tailings all entered the magnetic separation process. Although it was adjusted during the sorting process, the grade of iron fine powder only reached 36%-38 due to the influence of mud, and it seriously affected the filtration effect. The average water content of iron fine powder reached 25.7%.
High gradient magnetic mineral sorting process
(1) Red mud lifting process. The red mud raw material of the plant is pumped to the ore slurry tank through the discharge pipe of the aluminum plant. After the original slurry is diluted to the designed concentration, it is pumped to the grinding room for classification and fine grinding. The grinding product enters the strong magnetic machine for rough selection. The rough-selected tailings are then cleaned by a strong magnetic machine, and the concentrates at both ends enter the high-efficiency thickening machine. The dense products are dehydrated after the filtration process, and the products are run to the concentrate pool after dehydration.
(2) The semi-loaded, full-load industrial red mud iron test was carried out on the tailings of the tailings. The production parameters in the whole process of the whole process and the iron content of the alumina red mud slurry were carried out in each process. Analysis and comparison, the feed concentration of the original slurry in each process was tested and adjusted. Focus on how to improve the grade of iron powder in the rough selection and sweeping production process, and study various technical performance parameters and process parameters of the equipment, as shown in the following table (the data in the table are percentages):
number | Raw ore | Tailings | Fine powder | Fine powder | Fine powder | Fine powder |
project | SiO2 Fe2O3 Al2O3 | SiO2 Fe2O3 Al2O3 | SiO2 Fe2O3 Al2O3 | Moisture | Iron recovery rate | Ore yield |
1 2 3 4 5 6 7 8 9 10 average value | 17.6 50 13.3 21.32 40.72 13.85 22.33 40.36 15.5 20.01 32.5 20.1 22.45 33.57 19.6 27.5 41.08 13 21.25 32.14 20.65 21.13 33.76 15.9 22.93 36.43 17.3 20.29 31.79 20.8 21.68 37.2 17 | 29.66 35.36 14 25.09 31.45 20.4 19.81 37.86 18.75 25.33 28.25 20.3 28.7 25.18 18.9 32.06 25.43 19.9 22.69 28.93 20.9 22.21 27.5 21.75 25.33 26.007 21 27.86 23.57 23.2 25.9 29 19.9 | 9.05 56 9.5 10.35 58 10.8 7.14 56.05 8.4 12.12 59 12.8 8.68 60 9 7.5 58 9.4 8.81 59 11.1 11.33 60 8.7 9.33 61 10.5 10.57 62 10.2 9.48 58.91 10.4 | 24.4 28.6 22.9 23.5 23.5 27.6 26.8 24.4 28.8 28 25.85 | 0.63 0.5 0.41 0.19 0.23 0.39 0.17 0.32 0.49 0.41 0.37 | 0.48 0.23 0.14 0.11 0.18 0.41 0.08 0.17 0.29 0.21 0.23 |
|
Primary industrial test red mud selection iron full magnetic separation process
Through the full magnetic separation process, the first red mud full magnetic separation industrial test, the average grade of iron fine powder is 41%, and in the case of increasing production in the later stage, the average grade of iron fine powder is only 38%. The product contains more mud, which directly affects the filtration effect of the fine powder. The average moisture content of the fine powder is 25.85%, which does not meet the design specifications of the process.
3 Red mud full magnetic selection iron process optimization
After the first red mud full magnetic separation iron industry experiment analysis, the red mud particle size composition has a great influence on magnetic separation and filtration. To this end, the raw materials entering the roughing pre-distributor and the tailings selected for sweeping were analyzed by grain size, as shown in the following table:
Through the analysis of the original ore slurry size of the incoming material, the fine grinding after the fine grinding, and the grain size analysis of the tailings, it is found that the 325 mesh fine particles account for a large proportion, affecting the selection of the SLon vertical ring pulsating high gradient magnetic machine. effect. The whole magnetic separation process has been optimized as follows: coarse subdivision level - thinning and coarsening - coarse material fine grinding - strong magnetic rough selection - fine refining tailing - rough tail re-election - tailing retention - concentrate coarse and dense - Filter and dehydrate.
| Granular grade /mesh | quality /g | Mass ratio /g | TFe grade /% | Remarks |
Distributor | +80 —80+120 —120+200 —200 total | 90.0 50.0 40.5 290.2 470.7 | 19.12 10.62 8.6 61.65 100.00 | 30.17 31.87 29.38 17.42 | Material weight The concentration is 28.55%; Iron grade 22.54% |
Sweeping tailings | +200 —200+325 —325 total | 42.8 4.8 131.6 179.6 | 2.68 23.89 73.43 100 | 20 19 17 18.6 | Material weight Concentration 12.69%; Iron grade 18% |
Process optimization
1. Full magnetic separation process optimization adjustment
Through one month of industrial experiments, the selection criteria for iron fines of the products are shown in the table (the data in the table are percentages)
ingredient | TFe | SiO2 | FeO | Al2O3 | Na2O | CaO | Moisture | Iron recovery rate |
content | 41.23 | 9.48 | 0.35 | 10.04 | 3.21 | 2.6 | 25.85 | 37 |
2. Cyclone grading and thinning optimization
In the magnetic separation process, due to the muddy of part of the slurry, the viscosity of the slurry is increased, the inclusions, encapsulation and adsorption of the gangue minerals in the concentrate product are serious, the quality of the concentrate slurry is reduced, and the workload of the thickener is increased. The working conditions are deteriorated, so that the particles are too slow in the sedimentation process, and the muddy slurry is difficult to be concentrated by natural sedimentation, which causes the pulp to return to the slurry.
The ultrafine muddy part affects the selection of the vertical ring pulsation high gradient magnetic machine and the filtration of the iron fine powder, and the process is optimized. The pre-grinding process is changed to a coarse subdivision level - thinning and thickening. The ultra-fine muddy part is directly entered into the tailings pond, and does not participate in the sorting operation. The coarse-grained grade is finely ground and then enters the next process.
After trial production, the quality index of iron concentrate has been greatly improved. The sorting effect of the iron fine powder is shown in the following table (the data in the table are percentages):
ingredient | TFe | SiO2 | FeO | Al2O3 | Na2O | CaO | Moisture | Iron recovery rate |
content | 48 | 10 | 0.35 | 10.04 | 3.21 | 2.6 | 18 | 37 |
After the process optimization, after many trial production tests, the grade of iron fine powder is basically stable above 48%, the highest can be increased to 52%, and the water content is stable below 18%, which basically achieves the purpose of process optimization.
4 Conclusion
(1) SLon vertical ring pulsation high gradient magnetic machine is better in the red mud iron project. The device has a unique magnetic medium structure and is not easy to block; relying on effective pulsation to keep the particles in a loose state during the process of selecting particles, it can effectively eliminate the mechanical inclusions of non-magnetic particles, and effectively adjust the liquid level, stroke and rush. The characteristics of operability such as secondary and exciting current have greatly improved the mineral processing index. The final grade of fine iron powder increased from 38.00% to 52%, an increase of 14%.
(2) A number of tests were carried out on the fractional composition of the ore slurry of the tailings, and the content of the muddy fraction of the red mud fraction was higher. After the grading and fine grinding, the red mud tailings all entered the magnetic separation process. Although it was adjusted during the sorting process, the grade of the iron fine powder of the product only reached 36%-38% due to the influence of mud. Affecting the filtration effect of the product, the product iron fine powder has an average water content of 25.%. Therefore, it is considered that the ultra-fine muddy part directly affects the sorting effect of the vertical ring pulsation high gradient magnetic machine and affects the filtration effect of the iron fine powder.
(3) After the optimization of the red mud full magnetic separation process, the equipment process and the slurry pipeline are rationalized, and the harmful tailings are successfully transformed into objective economic benefits, and the red mud waste is rationally utilized and disposed of harmlessly. It has specific theoretical and practical significance.
CT-C Hot Air Tray Dryer is an industrial dryer which is widly used
for drying operations in the pharmaceutical, chemical, food,
light industry, heavy industry, and other industries
Applications
Our CT-C hot air circulating oven is an industrial dryer which is extensively
used for thermosetting and drying operations in the pharmaceutical, chemical,
food, light industry, heavy industry, and other industries. Some of the
materials and products that are usually dried by it include raw material
medicine, crude drug, traditional Chinese medicine, powder, particle, pigment,
dyestuff, dehydrated vegetable, dried fruit, sausage, plastic resin, electric
elements, baking finish, etc.
Features
Yutong CT-C hot air circulating oven is suitable for various kinds of materials
Most hot air is circulated inside the oven, resulting in high thermal
efficiency
Wide selection of heat source, including steam, heat conduction oil,
electricity, hot water, far infrared
Wide temperature range, from atmospheric temperature to 350℃
Low noise, automatic temperature control, smooth operation, easy installation,
simple maintenance
Technical Specifications of CT-C Hot Air
Circulating Oven
|
Model
|
CT-C-O
|
CT-C-I
|
CT-C-II
|
CT-C-IIA
|
CT-C-III
|
CT-C- IIIA
|
CT-C-IV
|
|
Dried weight per lot(kg/lot)
|
60
|
120
|
240
|
240
|
360
|
360
|
480
|
|
Evaporation area(m2)
|
7.1
|
14.1
|
28.3
|
28.3
|
42.4
|
42.4
|
56.5
|
|
Radiator area(m2)
|
15
|
24
|
48
|
48
|
72
|
72
|
96
|
|
Steam consumption(kg/h)
|
15
|
20
|
40
|
40
|
60
|
60
|
80
|
|
Electric heating power(kw)
|
6-9
|
15
|
30
|
30
|
45
|
45
|
60
|
|
Fan flow(m2/h)
|
3450
|
3450
|
6900
|
6900
|
10350
|
10350
|
13800
|
|
Fan power(kw)
|
0.45
|
0.45
|
0.45×2
|
0.45×2
|
0.45×3
|
0.45×3
|
0.45×4
|
|
Temp. tolerance inside oven(℃ )
|
±1
|
±2
|
±2
|
±2
|
±2
|
±2
|
±2
|
Hot Air Circulating Tray Dryer
Hot Air Tray Dryer,Hot Air Circulation Drying Oven,Fruit De-Water Drying Machine,Circulating Tray Dryer
Jiangsu Yutong Drying Engineering Co.,Ltd , http://www.ytdryer.com