CN116282033A - Preparation method of honeycomb reduction pellets for industrial silicon - Google Patents
Preparation method of honeycomb reduction pellets for industrial silicon Download PDFInfo
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- 239000008188 pellet Substances 0.000 title claims abstract description 146
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 91
- 239000010703 silicon Substances 0.000 title claims abstract description 86
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000003245 coal Substances 0.000 claims abstract description 315
- 239000011230 binding agent Substances 0.000 claims abstract description 205
- 239000002245 particle Substances 0.000 claims abstract description 118
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 85
- 238000003756 stirring Methods 0.000 claims abstract description 53
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 42
- 238000002156 mixing Methods 0.000 claims abstract description 34
- 239000011248 coating agent Substances 0.000 claims abstract description 32
- 238000000576 coating method Methods 0.000 claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000001816 cooling Methods 0.000 claims abstract description 11
- 238000005253 cladding Methods 0.000 claims abstract description 5
- 239000011247 coating layer Substances 0.000 claims description 134
- 239000002131 composite material Substances 0.000 claims description 59
- 238000000034 method Methods 0.000 claims description 28
- 235000019353 potassium silicate Nutrition 0.000 claims description 22
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical group [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 22
- 239000002994 raw material Substances 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 11
- 239000010410 layer Substances 0.000 claims description 9
- 238000000465 moulding Methods 0.000 claims description 6
- 229920002472 Starch Polymers 0.000 claims description 2
- -1 and so on Substances 0.000 claims description 2
- 235000019698 starch Nutrition 0.000 claims description 2
- 238000003723 Smelting Methods 0.000 abstract description 18
- 238000004939 coking Methods 0.000 abstract description 11
- 239000003575 carbonaceous material Substances 0.000 abstract description 5
- 230000009257 reactivity Effects 0.000 abstract description 2
- 229920000881 Modified starch Polymers 0.000 description 20
- 239000004368 Modified starch Substances 0.000 description 20
- 235000019426 modified starch Nutrition 0.000 description 20
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
- 239000003638 chemical reducing agent Substances 0.000 description 12
- 239000000377 silicon dioxide Substances 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000007873 sieving Methods 0.000 description 5
- 239000003610 charcoal Substances 0.000 description 4
- 230000035699 permeability Effects 0.000 description 3
- 239000002006 petroleum coke Substances 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 241000609240 Ambelania acida Species 0.000 description 1
- 235000017060 Arachis glabrata Nutrition 0.000 description 1
- 241001553178 Arachis glabrata Species 0.000 description 1
- 235000010777 Arachis hypogaea Nutrition 0.000 description 1
- 235000018262 Arachis monticola Nutrition 0.000 description 1
- 239000010905 bagasse Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002802 bituminous coal Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 235000020232 peanut Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/023—Preparation by reduction of silica or free silica-containing material
- C01B33/025—Preparation by reduction of silica or free silica-containing material with carbon or a solid carbonaceous material, i.e. carbo-thermal process
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
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Abstract
The invention relates to a preparation method of honeycomb reduction pellets for industrial silicon, and belongs to the technical field of efficient clean utilization of resources. The honeycomb reduction pellet for the industrial silicon is prepared by taking coking coal with different particle sizes as a carbonaceous material, mixing and stirring the coking coal with water and a binder, coating the coking coal into a honeycomb shape layer by layer, then roasting the honeycomb reduction pellet for the industrial silicon at the low temperature of 400-600 ℃ for 2-4 hours while isolating air, and cooling the honeycomb reduction pellet for the industrial silicon. According to the invention, coking coal is used as a carbonaceous material, and the porous honeycomb structure is formed by layer-by-layer cladding after mixing and stirring by utilizing the combination of different particle sizes and binding properties, and the density, the porosity and the fixed carbon content of the pellets are improved by roasting the coking coal. The honeycomb reduction pellet for industrial silicon has high fixed carbon content, good reactivity, low ash content, high specific resistance and low cost; the honeycomb reduction pellet for industrial silicon is applied to industrial silicon smelting, the carbon burning loss rate is reduced by 8% -12%, and the silicon yield is improved by 4% -8%.
Description
Technical Field
The invention relates to a preparation method of honeycomb reduction pellets for industrial silicon, and belongs to the technical field of efficient clean utilization of resources.
Background
The silicon smelting in China mainly comprises mixing two or more raw materials of coal, petroleum coke, semicoke, blue carbon, charcoal, wood blocks (bagasse, peanut shells and the like) and the like according to a certain proportion to serve as carbonaceous raw materials. The production of industrial silicon can be classified into a full-coal process, a half-coal semicoke process, and the like according to the use of carbonaceous reducing agents. The whole coal process uses clean coal as carbonaceous reducing agent, and the semi-coal semicoke uses charcoal, bituminous coal, petroleum coke and the like as reducing agent. Although charcoal has better reducibility, the charcoal is not environment-friendly, and petroleum coke can be used as a carbonaceous reducing agent, the graphitization degree is high along with the increase of the calcination temperature, the conductivity is enhanced, and the specific resistance is rapidly reduced; and the furnace surface crust is serious to influence the air permeability of furnace charge, the fire is serious, and the furnace condition is not easy to control. So the future development direction is to take full coal as the main material. However, the ash content of the coal is high, the pyrolysis affects the air permeability of furnace burden at high temperature, so that the utilization rate of carbon raw materials is reduced, the heated area in the furnace is increased in ash and coking, and the furnace slag is increased, thereby easily causing the problems of rising furnace bottom and the like. Therefore, research and development of a novel reducing agent for industrial silicon smelting is a necessary path for the development of the silicon industry.
Disclosure of Invention
Aiming at the problems of reducing agent preparation in industrial silicon smelting in the prior art, the invention provides a preparation method of honeycomb reduction pellets for industrial silicon, which takes coking coal as a carbonaceous material, and utilizes the combination of different particle sizes and bonding properties to mix and stir for the first time and then coat layer by layer to form a porous honeycomb structure, and the density, the porosity and the fixed carbon content of the pellets are improved by roasting the coking coal, so that the pellets reach a certain bonding index. The honeycomb reduction pellet for industrial silicon has the reaction activity of more than 99 percent at 1000 ℃, the fixed carbon content of more than 75 percent, the volatile content of 12-20 percent, the ash content of less than 4 percent and the specific resistance of 3000-4000 omega m.
The invention discloses a preparation method of honeycomb reduction pellets for industrial silicon, which comprises the following steps:
step one preparation of center honeycomb pellets
The raw materials used for the central honeycomb pellet comprise low-viscosity coal and medium-viscosity coal, wherein the particle size of the low-viscosity coal is 5-15mm, the bonding index is less than or equal to 20, the particle size of the medium-viscosity coal is 0.2-0.6mm, and the bonding index is 50-65;
when the central honeycomb pellets are prepared, the mass ratio of the low-viscosity coal to the medium-viscosity coal is 40-50:30-40;
adding low-viscosity coal into medium-viscosity coal, mixing, stirring uniformly, adding 8-12 wt.% of water, and 0.8-1.2wt.%, preferably 1wt.% of binder, stirring until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 20-30 mm;
step two cladding
Selecting high-viscosity coal with different particle sizes and binding indexes, and coating the central honeycomb pellets layer by layer; coating a 1 st coating layer on the central honeycomb pellet, coating a 2 nd coating layer on the 1 st coating layer, and so on, coating an i+1 th coating layer on the i th coating layer; obtaining formed agglomerate particles;
wherein i is a positive integer of 1 or more; the bonding index of the high-viscosity coal used by the ith coating layer is smaller than that of the high-viscosity coal used by the (i+1) th coating layer; the diameter of the high-viscosity coal used by the ith coating layer is larger than the viscosity diameter of the high-viscosity coal used by the (i+1) th coating layer; the diameter of the high-viscosity coal used by the ith coating layer is smaller than that of the medium-viscosity coal used by the central honeycomb pellet;
wherein, the mass ratio of the low-viscosity coal used for the center honeycomb pellet to the high-viscosity coal used for the first coating layer of the medium-viscosity coal used for the center honeycomb pellet is 40-50:30-40:20-30;
the mass ratio of the high-viscosity coal used for the first coating layer to the high-viscosity coal used for the second coating layer is 20-30:20-30;
the grain diameter of the high-viscosity coal used for the first coating layer is 0.05-0.1mm, and the bonding index is 70-85; the particle size of the high-viscosity coal used for the second coating layer is 0.02-0.05mm, and the bonding index is more than 85.
And thirdly, placing the agglomerate particles formed in the second step into an air-isolated low-temperature roasting furnace at 400-600 ℃ for 2-4 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The coal used in the present invention is preferably coking coal. Of course other carbonaceous materials may be used in the present invention.
Preferably, the invention can also introduce low-viscosity coal when preparing any coating layer; the granularity and the bonding index of the introduced low-viscosity coal and the low-viscosity coal used for preparing the central honeycomb pellets are basically consistent. Namely, when any coating layer is prepared, low-viscosity coal can be introduced; the particle size of the low-viscosity coal is 5-15mm, and the caking index is less than or equal to 20.
Preferably, when any coating layer is prepared, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the coating layer is 20-50:50-80. In the invention, when any coating layer is prepared, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the layer is controlled to be 20-50:50-80 is because the bonding index of the prepared honeycomb reduction pellets needs to be controlled within the range of 60-80, and the cold strength is controlled within the range of 8-14 MPa; if the proportion of the introduced low-viscosity coal is too high, the pellets are easy to crack and fall off powder, so that raw material waste is caused; too low a voltage will result in increased power consumption, increased energy loss and increased cost.
As a further preference, in the preparation of the coating layer 1, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the coating layer is 20-50:50-80. Preferably 30-50:50-70.
As a further preference, in the preparation of the coating layer 2, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the coating layer is 20-50:50-80. Preferably 20-40:60-80.
As a further preferable scheme, the particle size of the low-viscosity coal used for the central honeycomb pellets is 7mm, the caking index is 5, the particle size of the medium-viscosity coal used is 0.3mm, and the caking index is 55; the particle size of the high-viscosity coal used for the first coating layer is 0.06mm, and the bonding index is 75; the particle size of the high-viscosity coal used for the second coating layer is 0.025mm, and the bonding index is 90.
The mass ratio of the low-viscosity coal used for the center honeycomb pellets, the medium-viscosity coal used for the center honeycomb pellets, the high-viscosity coal used for the first coating layer and the high-viscosity coal used for the second coating layer is 45:30:30:25.
As a further preferable scheme, the particle size of the low-viscosity coal used for the honeycomb pellets is 8mm, the caking index is 15, the particle size of the medium-viscosity coal used is 0.3mm, and the caking index is 60; the particle size of the high-viscosity coal used for the first coating layer is 0.065mm, and the bonding index is 70; the particle size of the highly viscous coal used for the second coating layer was 0.044mm, and the caking index was 94.
The mass ratio of the low-viscosity coal used for the center honeycomb pellets, the medium-viscosity coal used for the center honeycomb pellets, the high-viscosity coal used for the first coating layer and the high-viscosity coal used for the second coating layer is 40:35:25:25.
As a further preferable scheme, the particle size of the low-viscosity coal used for the central honeycomb pellets is 10mm, the caking index is 10, the particle size of the medium-viscosity coal used is 0.4mm, and the caking index is 64; the particle size of the high-viscosity coal used for the first coating layer is 0.075mm, and the bonding index is 80; the particle size of the high-viscosity coal used for the second coating layer is 0.037mm, and the bonding index is 96.
The mass ratio of the low-viscosity coal used for the center honeycomb pellets, the medium-viscosity coal used for the center honeycomb pellets, the high-viscosity coal used for the first coating layer and the high-viscosity coal used for the second coating layer is 50:35:30:25.
Further, the honeycomb reduction pellet for industrial silicon, when i=2, is prepared by the steps of:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 6-12mm, and the caking index is 5-20; the particle size of the medium caking coal is 0.3-0.5mm, and the caking index is 55-65; the grain diameter of the high-viscosity coal used for the first coating layer is 0.06-0.1mm, and the bonding index is 70-85; the particle size of the high-viscosity coal used for the second coating layer is 0.02-0.045mm, and the bonding index is more than 85.
Step 2, adding low-viscosity coal into the medium-viscosity coal according to the mass ratio of 40-50: mixing and stirring evenly 30-40, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.% of binder, preferably 1wt.% to obviously agglomerate, and forming into a central honeycomb pellet with the diameter of 20-30 mm;
step 3, mixing low-viscosity coal and high-viscosity coal used for the first coating layer according to a mass ratio of 30-50:50-70, adding the central honeycomb pellets in the step 2, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1wt.% of binder until the binder is obviously agglomerated, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 30-50 mm;
step 4, mixing the low-viscosity coal and the high-viscosity coal used for the second coating layer according to the mass ratio of 20-40:60-80, adding the agglomerate particles in the step 3, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1wt.% of binder until the binder is obviously agglomerated, and coating and molding the central honeycomb pellets in the step 3 into agglomerate particles with the diameter of 50-60 mm;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 400-600 ℃ for 2-4 hours, and cooling to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The fixed carbon content of the four coals with different caking indexes in the step 1 is 55 to 68 wt%.
The binder in the steps 2,3 and 4 is an organic-inorganic composite binder, wherein the inorganic binder accounts for 20-40 wt% of the composite binder, and the organic binder accounts for 60-80 wt%. The inorganic binder is selected from water glass; the organic binder is selected from the group consisting of textured starches.
The bonding index of the composite bonding coal reduction pellet for the industrial silicon prepared by the method is 60-80, and the cold strength is 8-14 MPa.
In the present invention, the silicon yield refers to the ratio of 1t to the mass of silica (t) consumed to produce one ton of silicon. The silicon yield = 1 t/silica unit consumption 100%.
The process of the invention is adopted; the silicon yield is 38.9% -43.1% and the purity of the obtained industrial silicon is more than or equal to 99.3%.
After optimization, the silicon yield is 43.1% and the silicon purity is 99.6% by weight.
The beneficial effects of the invention are as follows:
1. according to the invention, coking coal is used as a carbonaceous raw material, and the porous honeycomb structure is formed by layer-by-layer cladding after mixing and stirring by utilizing the combination of different particle sizes and bonding properties, and the smaller the particle size is, the higher the bonding effect is, so that a large number of gaps exist in the particles, the full dispersion in smelting is facilitated, and the full combustion of the carbon material is ensured.
2. According to the invention, the density, the porosity and the fixed carbon content of the pellets are improved by roasting the coking coal, meanwhile, the honeycomb-shaped reduction pellets reach a certain bonding index by increasing the temperature, and finally, the porous honeycomb-shaped structure with higher strength is formed, so that the permeability of furnace burden in smelting can be ensured, the carbon burning loss rate is reduced by 8% -12%, and the silicon yield is improved by 4% -8%.
3. The honeycomb-type reduction pellets for industrial silicon prepared by the method are released in a large amount of volatile matters after roasting, the reactivity reaches over 99 percent at 1000 ℃, the fixed carbon content reaches over 75 percent, the volatile matter content is 12-20%, the ash content is low and is lower than 4%, the specific resistance is 3000-4000 Ω & m, the cold strength reaches 8-14 MPa, and the bonding index reaches 60-80, and can be completely suitable for industrial silicon.
Detailed Description
The invention will be described in further detail with reference to specific embodiments, but the scope of the invention is not limited to the description.
In the steps 3 and 4 of the embodiment of the invention, all the low-viscosity coals and the low-viscosity coals in the steps 1 and 2 of the corresponding embodiment are the same batch.
Example 1
The honeycomb reduction pellet for industrial silicon has a fixed carbon content of 77.4wt.%, a volatile content of 19wt.%, an ash content of 3.6wt.%, a specific resistance of 3500 Ω·m, a junction index G of 70 and a pellet cold strength of 11MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 10mm, and the caking index is 5; the particle size of the medium caking coal is 0.3mm, and the caking index is 55; the particle size of the high-viscosity coal used for the first coating layer is 0.06mm, and the bonding index is 75; the particle size of the high-viscosity coal used for the second coating layer is 0.02mm, and the bonding index is 93; the mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 45:35:25:25.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 45:35, adding 10wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 25 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating = 40:60, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 10wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 40 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for second coating = 35:65, adding the agglomerate particles in the step 3 after uniformly mixing and stirring, adding 10wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating and molding the central honeycomb pellets in the step 3 into agglomerate particles with the diameter of 50 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 500 ℃ for 3 hours, and cooling to room temperature along with the furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the fixed carbon content of the low-viscosity coal was 63wt.%, the volatile content was 32.6wt.%, and the ash content was 1wt.%
The fixed carbon content of the middle caking coal is 59wt.%, the volatile content is 36.7wt.%, and the ash content is 1.2wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 55wt.%, a volatile content of 38.2wt.%, and an ash content of 0.5wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 64wt.%, a volatile content of 32.2wt.%, and an ash content of 0.9wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 0.05% CaO) into blocks with the granularity of 25-100 mm, and then is compounded with 103kg after cleaning and sievingThe carbonaceous reducing agent is evenly mixed and added into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), the silicon yield is 40.4 percent, and the components of the industrial silicon product are Si>99.4Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Example 2
The honeycomb reduction pellet for industrial silicon has a fixed carbon content of 77.5wt.%, a volatile content of 20wt.%, an ash content of 2.8wt.%, a specific resistance of 4000 Ω·m, a caking index G of 74 and a pellet cold strength of 13MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 8mm, and the caking index is 10; the particle size of the medium caking coal is 0.35mm, and the caking index is 60; the particle size of the high-viscosity coal used for the first coating layer is 0.065mm, and the bonding index is 80; the particle size of the high-viscosity coal used for the second coating layer is 0.037mm, and the bonding index is 90. The mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 40:30:25:20.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 40:30, mixing and stirring uniformly, adding 11wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into a central honeycomb pellet with the diameter of 30 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating = 35:65, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 11wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 45 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the second coating layer = 20:80, after uniformly mixing and stirring, adding the agglomerate particles in the step 3, adding 11wt.% of water, stirring 1wt.% of binder until the agglomerate is obvious, and coating and molding the central honeycomb pellets in the step 3 into the agglomerate particles with the diameter of 55 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 550 ℃ for 2 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the low-viscosity coal had a fixed carbon content of 64wt.%, a volatile content of 34.6wt.%, and an ash content of 0.8wt.%
The fixed carbon content of the middle caking coal is 60wt.%, the volatile content is 35.7wt.%, and the ash content is 1wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 56wt.%, a volatile content of 37.2wt.%, and an ash content of 0.4wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 58wt.%, a volatile content of 36.2wt.%, and an ash content of 0.6wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 Crushing 0.05% CaO into blocks with the granularity of 25-100 mm, cleaning, sieving, uniformly mixing with 103kg of the composite carbonaceous reducing agent, adding into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), and obtaining a silicon yield of 43.1%, wherein the components of an industrial silicon product are Si>99.6Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Example 3
The honeycomb reduction pellet for industrial silicon has a fixed carbon content of 78.5wt.%, a volatile content of 18.2wt.%, an ash content of 3.3wt.%, a specific resistance 3800 Ω·m, a caking index G of 68 and a pellet cold strength of 10MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 12mm, and the caking index is 13; the particle size of the medium caking coal is 0.5mm, and the caking index is 61; the particle size of the high-viscosity coal used for the first coating layer is 0.08mm, and the bonding index is 82; the particle size of the high-viscosity coal used for the second coating layer is 0.045mm, and the bonding index is 89. The mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 50:40:30:25.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 50:40, uniformly mixing and stirring, adding 12wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into a central honeycomb pellet with the diameter of 30 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating=45: 55, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 12wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 48 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the second coating layer = 40:60, after uniformly mixing and stirring, adding the agglomerate particles in the step 3, adding 12wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating and molding the central honeycomb pellets in the step 3 into the agglomerate particles with the diameter of 60 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 500 ℃ for 4 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the low-viscosity coal had a fixed carbon content of 59wt.%, a volatile content of 35.6wt.%, and an ash content of 1.1wt.%
The fixed carbon content of the middle caking coal is 63wt.%, the volatile content is 34.7wt.%, and the ash content is 1.2wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 62wt.%, a volatile content of 36.2wt.%, and an ash content of 0.6wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 64wt.%, a volatile content of 33.2wt.%, and an ash content of 0.4wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 Crushing 0.05% CaO into blocks with the granularity of 25-100 mm, cleaning, sieving, uniformly mixing with 103kg of the composite carbonaceous reducing agent, adding into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), and obtaining a silicon yield of 39.9%, wherein the components of an industrial silicon product are Si>99.4Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Example 4
The honeycomb reduction pellet for industrial silicon has fixed carbon content of 80.4wt.%, volatile matter content of 16wt.%, ash content of 3.6wt.%, specific resistance 3200 Ω & m, knot index G of 60 and pellet cold strength of 8MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 13mm, and the caking index is 8; the particle size of the medium caking coal is 0.45mm, and the caking index is 56; the particle size of the high-viscosity coal used for the first coating layer is 0.06mm, and the bonding index is 70; the particle size of the high-viscosity coal used for the second coating layer is 0.035mm, and the bonding index is 88. The mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 45:40:30:20.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 45:40, mixing and stirring uniformly, adding 8wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into a central honeycomb pellet with the diameter of 30 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating=50: 50, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 8wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 45 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the second coating layer = 40:60, after uniformly mixing and stirring, adding the agglomerate particles in the step 3, adding 8wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating and molding the central honeycomb pellets in the step 3 into agglomerate particles with the diameter of 50 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 400 ℃ for 4 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the fixed carbon content of the low-viscosity coal was 68wt.%, the volatile content was 30.6wt.%, and the ash content was 0.6wt.%
The fixed carbon content of the middle caking coal is 60wt.%, the volatile content is 34.7wt.%, and the ash content is 1.8wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 59wt.%, a volatile content of 36.2wt.%, and an ash content of 0.8wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 63wt.%, a volatile content of 33.2wt.%, and an ash content of 0.4wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 Crushing 0.05% CaO into blocks with the granularity of 25-100 mm, cleaning, sieving, uniformly mixing with 100kg of the composite carbonaceous reducing agent, adding into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), and obtaining a silicon yield of 38.9%, wherein the components of an industrial silicon product are Si>99.3Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Example 5
The honeycomb reduction pellet for industrial silicon has a fixed carbon content of 81.5wt.%, a volatile content of 14.8wt.%, an ash content of 3.7wt.%, a specific resistance of 3400Ω·m, a junction index G of 80 and a pellet cold strength of 14MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 12mm, and the caking index is 15; the particle size of the medium caking coal is 0.35mm, and the caking index is 65; the particle size of the high-viscosity coal used for the first coating layer is 0.075mm, and the bonding index is 75; the particle size of the high-viscosity coal used for the second coating layer is 0.025mm, and the bonding index is 93. The mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 50:30:30:30.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 50:30, uniformly mixing and stirring, adding 10wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into a central honeycomb pellet with the diameter of 28 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 40wt% of the organic-inorganic composite binder, the organic binder accounts for 60wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating = 30:70, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 10wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 50 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 40wt% of the organic-inorganic composite binder, the organic binder accounts for 60wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for second coating = 35:65, adding the agglomerate particles in the step 3 after uniformly mixing and stirring, adding 10wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and cladding the central honeycomb pellets in the step 3 into agglomerate particles with the diameter of 60 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 40wt% of the organic-inorganic composite binder, the organic binder accounts for 60wt%, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 600 ℃ for 2 hours, and cooling to room temperature along with the furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the fixed carbon content of the low-viscosity coal was 65wt.%, the volatile content was 31.6wt.%, and the ash content was 1.4wt.%
The fixed carbon content of the middle caking coal is 63wt.%, the volatile content is 33.7wt.%, and the ash content is 1wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 60wt.%, a volatile content of 35.2wt.%, and an ash content of 0.7wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 68wt.%, a volatile content of 30.2wt.%, and an ash content of 0.6wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 Crushing 0.05% CaO into blocks with the granularity of 25-100 mm, cleaning, sieving, uniformly mixing with 103kg of the composite carbonaceous reducing agent, adding into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), the silicon yield is 41.5%, and the components of an industrial silicon product are Si>99.5Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Example 6
The honeycomb reduction pellet for industrial silicon has fixed carbon content of 79.8wt.%, volatile matter content of 16.8wt.%, ash content of 3.4%, specific resistance 3700 Ω·m, knot index G of 74 and pellet cold strength of 14MPa.
The preparation method of the honeycomb reduction pellet for the industrial silicon comprises the following steps:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 7mm, and the caking index is 14; the particle size of the medium caking coal is 0.35mm, and the caking index is 60; the particle size of the high-viscosity coal used for the first coating layer is 0.065mm, and the bonding index is 74; the particle size of the high-viscosity coal used for the second coating layer was 0.045mm, and the bonding index was 96. The mass ratio of the low-viscosity coal for preparing the center honeycomb pellets to the medium-viscosity coal for preparing the center honeycomb pellets to the high-viscosity coal for the first coating layer to the high-viscosity coal for the second coating layer is 40:35:30:30.
Step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 40:35, adding 12wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 27 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 3, low-viscosity coal and high-viscosity coal used by the first coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the first coating = 35:65, after uniformly mixing and stirring, adding the central honeycomb pellets in the step 2, adding 12wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 48 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
step 4, the low-viscosity coal and the high-viscosity coal used by the second coating layer are mixed according to the mass ratio, and the low-viscosity coal is mixed: high-viscosity coal for the second coating layer = 30:70, after uniformly mixing and stirring, adding the agglomerate particles in the step 3, adding 12wt.% of water, stirring 1wt.% of binder until obvious caking is achieved, and coating the central honeycomb pellets in the step 3 into the agglomerate particles with the diameter of 58 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 30wt% of the organic-inorganic composite binder, the organic binder accounts for 70wt%, the inorganic binder is water glass, and the organic binder is modified starch;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 550 ℃ for 3 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
The raw materials used are as follows:
the low-viscosity coal had a fixed carbon content of 59wt.%, a volatile content of 34.6wt.%, and an ash content of 1.8wt.%
The fixed carbon content of the middle caking coal is 60wt.%, the volatile content is 35.7wt.%, and the ash content is 0.7wt.%;
the high-viscosity coal used for the first coating layer had a fixed carbon content of 65wt.%, a volatile content of 33.2wt.%, and an ash content of 0.4wt.%.
The high-viscosity coal used for the second coating layer had a fixed carbon content of 59wt.%, a volatile content of 35.2wt.%, and an ash content of 0.8wt.%.
200kg of silica (99.5% SiO) 2 、0.05％Al 2 O 3 、0.03％Fe 2 O 3 Crushing 0.05% CaO into blocks with the granularity of 25-100 mm, cleaning, sieving, uniformly mixing with 100kg of the composite carbonaceous reducing agent, adding into a submerged arc furnace for smelting (the smelting temperature is 2200 ℃), and obtaining a silicon yield of 42.7%, wherein the components of an industrial silicon product are Si>99.6Wt.％，Fe≤0.19Wt.％，Al≤0.09Wt.％，Ca≤0.05Wt.％。
Comparative example 1
Otherwise, the same as in example 1, except that 4 kinds of coals were directly mixed; the results were: the silicon yield was 32.5%, and the composition of the industrial silicon product was 87.1wt.% Si.
Comparative example 2
Otherwise, the procedure is as in example 1, except that:
step 1, firstly, respectively crushing three kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 10mm, and the caking index is 5; the particle size of the high-viscosity coal used for the first coating layer is 0.06mm, and the bonding index is 75; the particle size of the high-viscosity coal used for the second coating layer is 0.02mm, and the bonding index is 93; the mass ratio of the low-viscosity coal for preparing the central honeycomb pellets, the high-viscosity coal for the first coating layer and the high-viscosity coal for the second coating layer is 45:25:25.
Step 2, adding 10wt.% of water into the medium-viscosity coal, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 25 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
the operation and parameters of steps 3,4, 5 are the same as in example 1;
the results were: the silicon yield was 35.1% and the composition of the industrial silicon product was 96.4wt.% Si.
Comparative example 3
Otherwise, the procedure is as in example 1, except that:
step 2, adding low-viscosity coal into the medium-viscosity coal, wherein the medium-viscosity coal is prepared by the following steps of: low caking coal = 20:40, mixing and stirring uniformly, adding 10wt.% of water, stirring 1wt.% of binder until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 25 mm; wherein the binder is an organic-inorganic composite binder, the inorganic binder accounts for 20wt% in the organic-inorganic composite binder, the organic binder accounts for 80wt% in the organic-inorganic composite binder, the inorganic binder is water glass, and the organic binder is modified starch;
the operation and parameters of steps 1, 3,4, 5 are the same as in example 1;
the results were: the silicon yield was 36.2% and the composition of the industrial silicon product was 97.1wt.% Si.
Comparative example 4
Otherwise, the procedure is as in example 1, except that:
in the step 3, low-viscosity coal is not added; the results were: the silicon yield was 34.3% and the composition of the industrial silicon product was 95.7wt.% Si.
Comparative example 5
Otherwise, the procedure is as in example 1, except that:
step 4, adding no low-viscosity coal; the results were: the silicon yield was 36.8%, and the composition of the industrial silicon product was 98.3wt.% Si.
While the present invention has been described in detail with reference to the specific embodiments thereof, the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.
Claims (10)
1. The preparation method of the honeycomb-shaped reduction pellet for the industrial silicon is characterized by comprising the following steps of:
step one preparation of center honeycomb pellets
The raw materials used for the central honeycomb pellet comprise low-viscosity coal and medium-viscosity coal, wherein the particle size of the low-viscosity coal is 5-15mm, the bonding index is less than or equal to 20, the particle size of the medium-viscosity coal is 0.2-0.6mm, and the bonding index is 50-65;
when the central honeycomb pellets are prepared, the mass ratio of the low-viscosity coal to the medium-viscosity coal is 40-50:30-40;
adding low-viscosity coal into medium-viscosity coal, mixing, stirring uniformly, adding 8-12 wt.% of water, and 0.8-1.2wt.%, preferably 1wt.% of binder, stirring until the binder is obviously agglomerated, and forming into central honeycomb pellets with the diameter of 20-30 mm;
step two cladding
Selecting high-viscosity coal with different particle sizes and binding indexes, and coating the central honeycomb pellets layer by layer; coating a 1 st coating layer on the central honeycomb pellet, coating a 2 nd coating layer on the 1 st coating layer, and so on, coating an i+1 th coating layer on the i th coating layer; obtaining formed agglomerate particles;
wherein i is a positive integer of 1 or more; the bonding index of the high-viscosity coal used by the ith coating layer is smaller than that of the high-viscosity coal used by the (i+1) th coating layer; the diameter of the high-viscosity coal used by the ith coating layer is larger than the viscosity diameter of the high-viscosity coal used by the (i+1) th coating layer; the diameter of the high-viscosity coal used by the ith coating layer is smaller than that of the medium-viscosity coal used by the central honeycomb pellet;
wherein, the mass ratio of the low-viscosity coal used for the center honeycomb pellet to the high-viscosity coal used for the first coating layer of the medium-viscosity coal used for the center honeycomb pellet is 40-50:30-40:20-30;
the mass ratio of the high-viscosity coal used for the first coating layer to the high-viscosity coal used for the second coating layer is 20-30:20-30;
the grain diameter of the high-viscosity coal used for the first coating layer is 0.05-0.1mm, and the bonding index is 70-85; the particle size of the high-viscosity coal used for the second coating layer is 0.02-0.05mm, and the bonding index is more than 85;
and thirdly, placing the agglomerate particles formed in the second step into an air-isolated low-temperature roasting furnace at 400-600 ℃ for 2-4 hours, and cooling the mixture to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
2. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: when any coating layer is prepared, low-viscosity coal is introduced; the granularity and the bonding index of the introduced low-viscosity coal are consistent with those of the low-viscosity coal used for preparing the central honeycomb pellets, namely, when any coating layer is prepared, the low-viscosity coal is introduced; the particle size of the low-viscosity coal is 5-15mm, and the caking index is less than or equal to 20.
3. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: when any coating layer is prepared, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the coating layer is 20-50:50-80.
4. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: in the preparation of the 1 st coating layer, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the layer is 20-50:50-80. Preferably 30-50:50-70.
5. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: in the preparation of the coating layer 2, the mass ratio of the introduced low-viscosity coal to the high-viscosity coal used for the coating layer is 20-50:50-80. Preferably 20-40:60-80.
6. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: the particle size of the low-viscosity coal used for the central honeycomb pellet is 7mm, the bonding index is 5, the particle size of the medium-viscosity coal used is 0.3mm, and the bonding index is 55; the particle size of the high-viscosity coal used for the first coating layer is 0.06mm, and the bonding index is 75; the particle size of the high-viscosity coal used for the second coating layer is 0.025mm, and the bonding index is 90.
7. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: the mass ratio of the low-viscosity coal used for the center honeycomb pellets, the medium-viscosity coal used for the center honeycomb pellets, the high-viscosity coal used for the first coating layer and the high-viscosity coal used for the second coating layer is 45:30:30:25.
8. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps:
the particle size of the low-viscosity coal used for the honeycomb pellets is 8mm, the bonding index is 15, the particle size of the medium-viscosity coal used is 0.3mm, and the bonding index is 60; the particle size of the high-viscosity coal used for the first coating layer is 0.065mm, and the bonding index is 70; the particle size of the high-viscosity coal used by the second coating layer is 0.044mm, the bonding index is 94, the mass ratio of the low-viscosity coal used by the center honeycomb pellet to the medium-viscosity coal used by the center honeycomb pellet to the high-viscosity coal used by the first coating layer to the high-viscosity coal used by the second coating layer is 40:35:25:25; or (b)
The particle size of the low-viscosity coal used for the central honeycomb pellet is 10mm, the bonding index is 10, the particle size of the medium-viscosity coal used is 0.4mm, and the bonding index is 64; the particle size of the high-viscosity coal used for the first coating layer is 0.075mm, and the bonding index is 80; the particle size of the high-viscosity coal used for the second coating layer is 0.037mm, the bonding index is 96, the mass ratio of the low-viscosity coal used for the center honeycomb pellet to the medium-viscosity coal used for the center honeycomb pellet to the high-viscosity coal used for the first coating layer to the high-viscosity coal used for the second coating layer is 50:35:30:25.
9. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: when i=2, it is prepared by the steps comprising:
step 1, firstly, respectively crushing four kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the low-viscosity coal is 6-12mm, and the caking index is 5-20; the particle size of the medium caking coal is 0.3-0.5mm, and the caking index is 55-65; the grain diameter of the high-viscosity coal used for the first coating layer is 0.06-0.1mm, and the bonding index is 70-85; the particle size of the high-viscosity coal used for the second coating layer is 0.02-0.045mm, and the bonding index is more than 85.
Step 2, adding low-viscosity coal into the medium-viscosity coal according to the mass ratio of 40-50: mixing and stirring evenly 30-40, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.% of binder, preferably 1wt.% to obviously agglomerate, and forming into a central honeycomb pellet with the diameter of 20-30 mm;
step 3, mixing low-viscosity coal and high-viscosity coal used for the first coating layer according to a mass ratio of 30-50:50-70, adding the central honeycomb pellets in the step 2, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1wt.% of binder until the binder is obviously agglomerated, and coating the central honeycomb pellets in the step 2 into agglomerate particles with the diameter of 30-50 mm;
step 4, mixing the low-viscosity coal and the high-viscosity coal used for the second coating layer according to the mass ratio of 20-40:60-80, adding the agglomerate particles in the step 3, adding 8-12 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1wt.% of binder until the binder is obviously agglomerated, and coating and molding the central honeycomb pellets in the step 3 into agglomerate particles with the diameter of 50-60 mm;
and 5, placing the agglomerate particles formed in the step 4 into an air-isolated low-temperature roasting furnace at 400-600 ℃ for 2-4 hours, and cooling to room temperature along with a furnace to obtain the honeycomb-shaped reduction pellets for the industrial silicon.
10. The method for preparing honeycomb reduction pellets for industrial silicon according to claim 1, wherein the method comprises the following steps: the fixed carbon content of the four coals with different caking indexes in the step 1 is 55 to 68wt.%;
the binder in the steps 2,3 and 4 is an organic-inorganic composite binder, wherein the inorganic binder accounts for 20-40 wt% of the composite binder, and the organic binder accounts for 60-80 wt%. The inorganic binder is selected from water glass; the organic binder is selected from the group consisting of textured starches;
the bonding index of the obtained composite bonding coal reduction pellet for industrial silicon is 60-80, and the cold strength is 8-14 MPa.
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