CN116282032B - Method for preparing pellets by coating silica particles with different caking coals for industrial silicon - Google Patents

Method for preparing pellets by coating silica particles with different caking coals for industrial silicon Download PDF

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CN116282032B
CN116282032B CN202310352781.XA CN202310352781A CN116282032B CN 116282032 B CN116282032 B CN 116282032B CN 202310352781 A CN202310352781 A CN 202310352781A CN 116282032 B CN116282032 B CN 116282032B
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coal
bonding
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silica
particle size
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CN116282032A (en
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陈正杰
王晓月
马文会
李绍元
伍继君
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Kunming University of Science and Technology
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/02Silicon
    • C01B33/021Preparation
    • C01B33/023Preparation by reduction of silica or free silica-containing material
    • C01B33/025Preparation by reduction of silica or free silica-containing material with carbon or a solid carbonaceous material, i.e. carbo-thermal process
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10Energy storage using batteries

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Abstract

The invention belongs to the technical field of efficient clean utilization of resources, and particularly relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon. The pellet takes silica and coal as raw materials, takes large-particle-size silica as a center, adds water and an adhesive into the bonded coal with different bonding indexes according to the rule of coating the large particles with the small particles for coating layer by layer, then is baked for 2-3 hours at the low temperature of 500-600 ℃ with air isolated, and is cooled to obtain the carbonaceous reducing agent pellet for industrial silicon. According to the invention, silica and coal are used as raw materials, the strength of the pellets is improved by the hardness of the silica, the pellets are combined into a more compact porous structure by roasting the bonding coal with different particle sizes, and the fixed carbon content of the pellets is improved. The pellet of the invention can ensure the ventilation of the furnace surface of the melting furnace, improve the chemical reaction rate, reduce the silicon loss by 4% -10%, and can produce high-quality industrial silicon, thus being completely used for smelting and producing the industrial silicon.

Description

Method for preparing pellets by coating silica particles with different caking coals for industrial silicon
Technical Field
The invention belongs to the technical field of efficient clean utilization of resources, and particularly relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon.
Background
Most of industrial silicon smelting is to mix coal, petroleum coke, charcoal and the like according to one or more arbitrary proportions as carbon raw materials. However, the charcoal is derived from the consumption of forest resources, and excessive trees are cut, so that the forest protection law is violated, and the greenhouse effect is increased. Petroleum coke is a byproduct of crude oil pyrolysis, has high fixed carbon content and low ash content, and can be used as an industrial silicon production reducing agent instead of charcoal. But the petroleum coke has low reaction performance, is easy to graphitize at high temperature, and is unfavorable for the production of industrial silicon. The specific resistance of the coal is large, and the coal is not easy to graphitize at high temperature, so that the coal can be used as a reducing agent for replacing charcoal in industrial silicon production. However, the ash content of the coal is very high, a large amount of ash content generated by pyrolysis is easy to cause a spark phenomenon at high temperature, so that slag in the furnace is increased, and the problems of rising of the furnace bottom and the like are easily caused. In addition, the coal contains more oxide impurities, and the unreasonable proportion of the coal in the raw materials can cause the increase of the impurity content in the silicon product. These problems can raise the energy consumption of industrial silicon smelting, increase carbon emission, and waste of manpower, material resources and financial resources, and more novel reducing agents need to be researched and developed to be applied to the field of silicon industry so as to solve the problems.
At present, a novel composite carbonaceous reducing agent is prepared by grinding petroleum coke and low-ash coal into powder, uniformly mixing, adding a binder and water, and pressing into pellets under the pressure condition of 5-10 MPa, wherein the obtained pellets have high fixed carbon content and good reactivity, but the method only adjusts the proportion of the reducing agent, reduces the waste of carbon raw materials, cannot reduce or reduce silicon loss, and the quality and the stability of the quality of the obtained products are still to be studied. And the biomass raw material is processed to obtain biomass charcoal, the biomass charcoal and petroleum coke are uniformly mixed, and the biomass charcoal is hot pressed into pellets to obtain the industrial silicon-carbon reducing agent, so that the reduction rate of silica is improved by utilizing the synergistic strengthening effect of biomass. However, the method does not treat petroleum coke, only reduces the use of charcoal to a certain extent, and does not solve the problems of low bonding index of the reducing agent, easy graphitization and extra energy consumption.
So far, no report is known that silica is coated with coal with different caking indexes in multiple layers before smelting silicon.
Disclosure of Invention
Aiming at the problems of the preparation of the industrial silicon smelting reducing agent in the prior art, the invention provides a method for preparing pellets by coating silica particles with different bonding coals. The pellet has high fixed carbon content, good reactivity, high strength and proper bonding index, can produce high-quality industrial silicon, and can be completely used for smelting and producing the industrial silicon.
The present invention was developed based on the previous study (e.g., patent 2023101425031) for further cost reduction and convenient control. When the particle size distribution and the caking index distribution of the coal used for the 1 st coating layer are narrowed, the invention also finds that the product quality is obviously improved compared with the product of CN2023101425031 under the same process condition when the invention processes the same batch of raw materials.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals in industrial silicon, which takes coal and silica as raw materials, is matched with water and a binder, and takes silica as a core to coat a bonding coal bed layer by layer to form pellets; and the coated bonding coal layer is more than or equal to 1;
Different bonding coals are coated with silica particles, including silica, a1 st bonding coal bed and a2 nd bonding coal bed; wherein the particle size of the silica is larger than the particle size of the coal used by the coating layer, and the particle size of the coal used by the 1 st layer of bonding coal bed is larger than the particle size of the coal used by the 2 nd layer of bonding coal bed; the caking index of the coal used by the 1 st layer caking coal is smaller than that of the coal used by the 2 nd layer caking coal bed; the particle size of the coal used for the i-th bonding coal bed is larger than that of the coal used for the i+1-th bonding coal bed; the caking index of the coal used for the i-th layer caking coal is smaller than that of the coal used for the i+1-th layer caking coal bed; the i is a positive integer greater than or equal to 1; wherein the 1 st bonded coal seam is directly coated on the core silica.
Preferably, the particle size of the coal used in the 1 st layer of the bonding coal bed is less than 1/4 of the particle size of the silica.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by industrial silicon, wherein a layer 2 bonding coal bed is coated on silica coated with a layer 1 bonding coal bed; by analogy, the i+1-th coating is coated on silica coated with an i-layer bond coat.
The invention relates to a method for preparing pellets by coating silica particles with industrial silicon by using different bonding coals, wherein the particle size of the silica is 8-20mm, siO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20%, and CaO is less than or equal to 0.20%. The invention uses the silica with the particle size of 8-20mm, which is because the particle with smaller particle size is applied to the preparation of the composite carbonaceous reducing agent pellet when the silica is crushed, thereby improving the utilization rate of raw materials. If the particle size of the silica particles is too large or too small, the required strength and bond index cannot be achieved after firing.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon, wherein the particle size of the coals used by a first coating layer is 0.1-2mm, and the bonding index is 50-75; the particle size of the coal used for the second coating layer is less than 0.1mm, and the caking index is 80-95.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by industrial silicon, which comprises the following steps of:
step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 10-15mm, the particle size of the 1 st layer of bonding coal is 0.1-2mm, preferably 0.2-1mm, the bonding index is 65-75, the particle size of the 2 nd layer of bonding coal is less than 0.1mm, and the bonding index is 85-95;
step 2, adding the 1 st layer of caking coal into the silica, adding 8-10 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1 wt.% of binder until the caking is obvious, and cladding the silica into agglomerate particles with the diameter of 30-40 mm;
Step 3, adding the agglomerate particles in the step 2 into the layer 2 caking coal, adding 8-10 wt.% of water, and stirring 0.8-1.2wt.%, preferably 1 wt.% of binder until obvious caking, and coating the agglomerate particles in the step 2 into agglomerate particles with the diameter of 50-70 mm;
And 4, placing the agglomerate particles formed in the step 3 into an air-isolated low-temperature roasting furnace at 500-600 ℃ for 2-3 hours, and cooling to room temperature along with a furnace to obtain the carbonaceous reducing agent pellets for industrial silicon.
Preferably, the thickness of the 1 st bonded seam is 30-40mm, preferably 40mm. The thickness of the 2 nd bonded seam is 50-70mm, preferably 65mm.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon, wherein in the step 1, the mass ratio of silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20-30:30-50:30-50.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon, wherein the particle size of the silica is 12mm; the particle size of the 1 st layer of bonding coal is 0.3mm, and the bonding index is 70; the particle size of the coal used for bonding the layer 2 coal is less than 0.1mm, and the bonding index is 94;
the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20:30:35.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon, wherein the particle size of the silica is 15mm; the particle size of the 1 st layer of bonding coal is 0.25mm, and the bonding index is 75; the particle size of the coal used for the first layer of caking coal is less than 0.1mm, and the caking index is 90;
The mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 25:35:50.
The invention relates to a method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon, wherein the particle size of the silica is 14mm; the particle size of the 1 st layer of bonding coal is 0.4mm, and the bonding index is 73; the particle size of the coal used for the first layer of caking coal is less than 0.1mm, and the caking index is 89;
the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:40:40.
The invention relates to a method for preparing pellets by coating silica particles with different caking coals by industrial silicon, wherein the fixed carbon content of two coals with different caking indexes in step 1 is 58-68 wt.%;
The adhesive in the step 2 and the step 3 is an organic-inorganic composite adhesive, wherein the inorganic adhesive accounts for 10-30 wt.% and the organic adhesive accounts for 70-90 wt.%; the inorganic binder is selected from water glass; the organic binder is a cellulosic binder.
The pellet bonding index obtained by the method for preparing the pellets by coating silica particles with different bonding coals by using the industrial silicon is 60-80, and the cold strength is 9-14 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; after smelting the pellets, the silicon yield is 39.2% -42.9% and the purity of the obtained industrial silicon is more than or equal to 99.3%.
After optimization, the silicon yield is 42.9% and the silicon purity is 99.6% by weight.
The beneficial effects of the invention are as follows:
1. According to the invention, silica and bonding coal are used as carbonaceous raw materials, the strength of the pellets is improved by the hardness of the silica, the silica is coated in the center, the contact surface of the coal and the silica is improved, and the silicon loss is reduced by 4% -10% in the silicon smelting process.
2. The pellets are combined into a more compact porous structure by roasting the bonding coal with different particle sizes, so that the fixed carbon content of the pellets is improved. Meanwhile, the temperature is increased to enable the pellets to reach a certain bonding index, so that the pellets are high in fixed carbon content, good in reactivity, suitable in bonding index and low in cost, and can be used for producing high-quality industrial silicon and can be completely used for smelting and producing the industrial silicon.
3. The volatile matters of the carbonaceous reducing agent pellets prepared by the method are released in a large amount after roasting, the fixed carbon content is more than 75 wt%, the volatile matters content is 15 wt% to 20 wt%, the ash content is less than 4 wt%, the cold strength is 9 to 14MPa, and the bonding index is 60 to 80, so that the carbonaceous reducing agent pellets can be completely suitable for industrial silicon.
4. The carbonaceous reducing agent pellets prepared by the invention are used in industrial silicon smelting, can increase the furnace surface air permeability, assist in sinking materials and reduce the occurrence of fire-piercing phenomenon, and the obtained industrial silicon has Si more than or equal to 99.3wt% and the obtained industrial silicon has Si more than or equal to 99.6wt% after optimization.
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.
Example 1
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon has a fixed carbon content of 78.4wt.%, a volatile content of 18wt.%, an ash content of 3.6wt.%, a caking index G of 69 and a pellet cold strength of 10MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 12mm, the particle size of the 1 st layer of bonding coal is 0.2mm, the bonding index is 65, the particle size of the 2 nd layer of bonding coal is 0.08mm, and the bonding index is 89; the mass ratio of the silica, the 1 st layer of bonding coal and the 2 nd layer of bonding coal is 25:30:45.
And 2, adding the 1 st layer of bonding coal into the silica, adding 10wt.% of water and 1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding the silica into agglomerate particles with the diameter of 30mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 10wt.% of the organic-inorganic composite bonding agent, the organic bonding agent accounts for 90 wt.% of the organic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 10wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into the agglomerate particles with the diameter of 55mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 10wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 90 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 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 carbonaceous reducing agent pellets for the industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
The fixed carbon content of the 1 st layer of caking coal is 59wt.%, the volatile content is 37.7wt.%, and the ash content is 1.3wt.%;
the layer 2 caking coal had a fixed carbon content of 67wt.%, a volatile content of 34.6wt.%, and an ash content of 0.4wt.%.
98Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 102kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable under the furnace condition, the silicon yield is 39.4%, the components of the industrial silicon product are Si >99.4 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 2
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon has a fixed carbon content of 77.5wt.%, a volatile content of 20wt.%, an ash content of 2.8wt.%, a caking index G of 78 and a pellet cold strength of 13MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 13mm, the particle size of the 1 st layer of bonding coal is 0.3mm, the bonding index is 75, the particle size of the 2 nd layer of bonding coal is 0.075mm, and the bonding index is 92; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20:40:45.
And 2, adding the 1 st layer of bonding coal into the silica, adding 9wt.% of water and1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding and forming the silica into agglomerate particles with the diameter of 35mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% of the organic bonding agent, the organic bonding agent accounts for 80 wt.% of the inorganic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 9wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into the agglomerate particles with the diameter of 60mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 80 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 into an air-isolated low-temperature roasting furnace at 550 ℃ for 2 hours, and cooling to room temperature along with the furnace to obtain the carbonaceous reducing agent pellets for the industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
The fixed carbon content of the 1 st layer of the caking coal is 60wt.%, the volatile content is 35.6wt.%, and the ash content is 1.4wt.%;
the layer 2 caking coal had a fixed carbon content of 58wt.%, a volatile content of 39.6wt.%, and an ash content of 0.4wt.%.
97Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 103kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable under the furnace condition, the silicon yield is 41.4%, the components of the industrial silicon product are Si >99.5 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 3
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon comprises the following steps of fixing carbon content to 80.4wt.%, volatile content to 17wt.%, ash content to 2.6wt.%, caking index G to 75 and pellet cold strength to 12MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 15mm, the particle size of the 1 st layer of bonding coal is 0.25mm, the bonding index is 70, the particle size of the 2 nd layer of bonding coal is 0.065mm, and the bonding index is 95; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:30:50.
And 2, adding the 1 st layer of bonding coal into the silica, adding 10wt.% of water and 1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding the silica into agglomerate particles with the diameter of 40mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% of the organic bonding agent, the organic bonding agent accounts for 80 wt.% of the inorganic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 10wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into agglomerate particles with the diameter of 65mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 80 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 into a furnace to cool to room temperature along with air-insulated low-temperature roasting for 2 hours at 600 ℃ to obtain the carbonaceous reducing agent pellets for industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
The fixed carbon content of the 1 st layer of caking coal is 62wt.%, the volatile content is 34.6wt.%, and the ash content is 1.2wt.%;
The layer 2 caking coal had a fixed carbon content of 65wt.%, a volatile content of 33.6wt.%, and an ash content of 0.5wt.%.
100Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 100kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable under the furnace condition, the silicon yield is 42.9%, the components of the industrial silicon product are Si >99.6 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 4
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon has a fixed carbon content of 82.5wt.%, a volatile content of 15wt.%, an ash content of 2.5wt.%, a caking index G of 60 and a pellet cold strength of 15MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 14mm, the particle size of the 1 st layer of bonding coal is 0.35mm, the bonding index is 68, the particle size of the 2 nd layer of bonding coal is 0.075mm, and the bonding index is 90; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20:50:30.
And 2, adding the 1 st layer of bonding coal into the silica, adding 8wt.% of water and1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding the silica into agglomerate particles with the diameter of 36mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 30 wt.% of the organic-inorganic composite bonding agent, the organic bonding agent accounts for 70 wt.% of the organic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 8wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into the agglomerate particles with the diameter of 58mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 30 wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 70 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 into a furnace to cool to room temperature along with air-insulated low-temperature roasting for 3 hours at 600 ℃ to obtain the carbonaceous reducing agent pellets for industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
the fixed carbon content of the 1 st layer of the caking coal is 68wt.%, the volatile content is 30.8wt.%, and the ash content is 0.8wt.%;
the layer 2 binder coal had a fixed carbon content of 65wt.%, a volatile content of 31.8wt.%, and an ash content of 1.2wt.%.
106Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 97kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable, the silicon yield is 39.2%, the components of an industrial silicon product are Si >99.3 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 5
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon comprises the steps of fixing carbon content to 80.1wt.%, volatile content to 16wt.%, ash content to 3.9wt.%, caking index G to 80 and pellet cold strength to 14MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 15mm, the particle size of the 1 st layer of bonding coal is 0.4mm, the bonding index is 75, the particle size of the 2 nd layer of bonding coal is 0.09mm, and the bonding index is 91; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:50:50.
And 2, adding the 1 st layer of bonding coal into the silica, adding 9wt.% of water and1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding the silica into agglomerate particles with the diameter of 38mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 10 wt.% of the organic-inorganic composite bonding agent, the organic bonding agent accounts for 90 wt.% of the organic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 9wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into agglomerate particles with the diameter of 70mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 10 wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 90 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 into an air-isolated low-temperature roasting furnace at 550 ℃ for 2 hours, and cooling to room temperature along with the furnace to obtain the carbonaceous reducing agent pellets for the industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
The fixed carbon content of the 1 st layer of the caking coal is 60wt.%, the volatile content is 35.9wt.%, and the ash content is 1.8wt.%;
the layer 2 caking coal had a fixed carbon content of 67wt.%, a volatile content of 30.1wt.%, and an ash content of 0.8wt.%.
100Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 100kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable, the silicon yield is 41.7%, the components of an industrial silicon product are Si >99.5 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 6
A method for preparing pellets by coating silica particles with different bonding coals for industrial silicon has a fixed carbon content of 79.8wt.%, a volatile content of 17.5wt.%, an ash content of 2.7wt.%, a caking index G of 71 and a pellet cold strength of 13MPa.
The method for preparing the pellets by coating silica particles with different bonding coals by using industrial silicon comprises the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 11mm, the particle size of the 1 st layer of bonding coal is 0.25mm, the bonding index is 73, the particle size of the 2 nd layer of bonding coal is 0.065mm, and the bonding index is 88; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:45:45.
And 2, adding the 1 st layer of bonding coal into the silica, adding 10wt.% of water and 1 wt.% of bonding agent, stirring until the bonding agent is obviously agglomerated, and cladding the silica into agglomerate particles with the diameter of 40mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% of the organic bonding agent, the organic bonding agent accounts for 80 wt.% of the inorganic bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 3, adding the agglomerate particles in the step 2 into the layer 2 bonding coal, adding 10wt.% of water, stirring 1 wt.% of bonding agent until the bonding agent is obviously agglomerated, and coating and forming the agglomerate particles in the step 2 into agglomerate particles with the diameter of 65mm, wherein the bonding agent is an organic-inorganic composite bonding agent, the inorganic bonding agent accounts for 20 wt.% in the organic-inorganic composite bonding agent, the organic bonding agent accounts for 80 wt.% in the organic-inorganic composite bonding agent, the inorganic bonding agent is water glass, and the organic bonding agent is cellulose bonding agent.
And 4, placing the agglomerate particles formed in the step 3 into a furnace to cool to room temperature along with air-insulated low-temperature roasting for 2 hours at 600 ℃ to obtain the carbonaceous reducing agent pellets for industrial silicon.
The raw materials used are as follows:
the chemical components of the silica are SiO 2≥99.55%、Fe2O3≤0.10%、Al2O3 is less than or equal to 0.20 percent, and CaO is less than or equal to 0.20 percent;
the fixed carbon content of the 1 st layer of the caking coal is 61wt.%, the volatile content is 35.7wt.%, and the ash content is 1.3wt.%;
The layer 2 binder coal had a fixed carbon content of 62wt.%, a volatile content of 34.9wt.%, and an ash content of 1wt.%.
100Kg of silica (99.5% SiO 2、0.05%Al2O3、0.03%Fe2O3 and 0.05% CaO) is crushed into blocks with the granularity of 20-100 mm, and the blocks are cleaned and sieved, are uniformly mixed with 100kg of the composite carbonaceous reducing agent, are added into a submerged arc furnace for smelting (the smelting temperature is 2300 ℃), the smelting is stable under the furnace condition, the silicon yield is 40.5%, the components of the industrial silicon product are Si >99.6 wt%, fe is less than or equal to 0.19 wt%, al is less than or equal to 0.09 wt%, and Ca is less than or equal to 0.05 wt%.
Example 7
Other conditions were identical to example 5 except that: step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 15mm, the particle size of the 1 st layer of bonding coal is 2mm, the bonding index is 75, the particle size of the 2 nd layer of bonding coal is 0.09mm, and the bonding index is 91; the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:50:50; the silicon yield is 39.8 percent, the content of industrial Si is more than 99.4 percent, the content of Fe is less than or equal to 0.19 percent, the content of Al is less than or equal to 0.09 percent, and the content of Ca is less than or equal to 0.05 percent
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 (7)

1. A method for preparing pellets by coating silica particles with different bonding coals by using industrial silicon is characterized in that: coal and silica are used as raw materials, water and binder are matched, and silica is used as a core to coat and bond the coal bed layer by layer, so that the coal bed is in a sphere shape; and the coated bonding coal layer is equal to 2;
Different bonding coals are coated with silica particles, including silica, a1 st bonding coal bed and a2 nd bonding coal bed; wherein the particle size of the silica is larger than the particle size of the coal used by the coating layer, and the particle size of the coal used by the 1 st layer of bonding coal bed is larger than the particle size of the coal used by the 2 nd layer of bonding coal bed; the caking index of the coal used by the 1 st layer caking coal is smaller than that of the coal used by the 2 nd layer caking coal bed; wherein the 1 st layer of bonding coal layer is directly coated on the core silica;
The 2 nd bonding coal layer is coated on the silica coated with the 1 st bonding coal layer;
the pellets are prepared by the following steps:
Step 1, firstly, respectively crushing silica and two kinds of coals with different caking indexes into particles with required granularity; wherein the particle size of the silica is 10-15mm, the particle size of the 1 st layer of bonding coal is 0.1-2mm, the bonding index is 65-75, the particle size of the 2 nd layer of bonding coal is less than 0.1mm, and the bonding index is 85-95;
Step 2, adding the 1 st layer of caking coal into the silica, adding 8-10 wt% of water and 0.8-1.2% of binder, stirring until obvious caking, and coating the silica into agglomerate particles with the diameter of 30-40 mm;
Step 3, adding the agglomerate particles in the step 2 into the layer 2 caking coal, adding 8-10 wt wt.% of water, and stirring 0.8-1.2wt.% of binder until obvious caking, and coating and forming the agglomerate particles in the step 2 into agglomerate particles with the diameter of 50-70 mm;
And 4, placing the agglomerate particles formed in the step 3 into an air-isolated low-temperature roasting furnace at 500-600 ℃ for 2-3 hours, and cooling to room temperature along with a furnace to obtain the carbonaceous reducing agent pellets for industrial silicon.
2. A method of preparing pellets of industrial silicon coated with silica particles of different binder coals as claimed in claim 1, wherein:
In the step 1, the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20-30:30-50:30-50.
3. A method of preparing pellets of industrial silicon coated with silica particles of different binder coals as claimed in claim 1, wherein:
The particle size of the silica is 12mm; the particle size of the 1 st layer of bonding coal is 0.3mm, and the bonding index is 70; the particle size of the coal used for bonding the layer 2 coal is less than 0.1mm, and the bonding index is 94;
the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 20:30:35.
4. A method of preparing pellets of industrial silicon coated with silica particles of different binder coals as claimed in claim 1, wherein:
the particle size of the silica is 15mm; the particle size of the 1 st layer of bonding coal is 0.25mm, and the bonding index is 75; the particle size of the coal used for the first layer of caking coal is less than 0.1mm, and the caking index is 90;
The mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 25:35:50.
5. A method of preparing pellets of industrial silicon coated with silica particles of different binder coals as claimed in claim 1, wherein:
the particle size of the silica is 14mm; the particle size of the 1 st layer of bonding coal is 0.4mm, and the bonding index is 73; the particle size of the coal used for the first layer of caking coal is less than 0.1mm, and the caking index is 89;
the mass ratio of the silica to the 1 st layer of bonding coal to the 2 nd layer of bonding coal is 30:40:40.
6. A method of preparing pellets of industrial silicon coated with silica particles of different binder coals as claimed in claim 1, wherein:
the fixed carbon content of the two coals with different caking indexes in the step 1 is 58 to 68wt.%;
The adhesive in the step 2 and the step 3 is an organic-inorganic composite adhesive, wherein the inorganic adhesive accounts for 10-30 wt.% and the organic adhesive accounts for 70-90 wt.%; the inorganic binder is selected from water glass; the organic binder is a cellulosic binder.
7. A method for preparing pellets of industrial silicon coated with silica particles of different binder coals according to any of claims 1-5, characterized in that: after smelting the obtained pellets, the silicon yield is 39.2-42.9 wt.%, and the purity of the obtained industrial silicon is more than or equal to 99.3wt.%.
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