Method for preparing composite reducing agent pellets for silicon smelting by full coal high value

Abstract

The present application relates to a kind of full coal high-value preparation silicon smelting composite reducing agent pellet method, belong to carbonaceous reducing agent pellet preparation technical field.The present application is broken to particle size less than 0.2mm by grinding to vacuum drying full coal pulverized coal;Coffee shell powder is added to NaOH solution and soaked and activated, and coffee shell binder is obtained by solid-liquid separation;Full coal pulverized coal, coffee shell binder, microsilica and silica powder are ground and mixed to obtain coal powder mixture;Coal powder mixture is formed by pressing to obtain cylindrical blank;Cylindrical blank is placed in argon atmosphere and microwave calcination is carried out, and it is cooled to room temperature with furnace to obtain silicon smelting composite reducing agent pellet.The strength of the silicon smelting composite reducing agent pellet of the present application is 9~13MPa, which meets the needs of industrial silicon production, and after industrial test of the pellet, the silicon yield can reach 40~70t / d, the power consumption is 10500~12000KW·h / t, and the carbon excess coefficient is 1.1~1.7.

Description

A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal Technical Field

[0001] This invention relates to a method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, belonging to the field of carbonaceous reducing agent pellet preparation technology. Background Technology

[0002] Currently, the main technology for industrial silicon production, both domestically and internationally, involves feeding materials into a submerged arc furnace, where they undergo a carbothermic reduction reaction followed by refining. The materials used in smelting include silica and carbonaceous reducing agents, with the carbonaceous reducing agents primarily comprising...

[0003] Petroleum coke, charcoal, semi-coke, and coal are among the materials used in industrial production. Different carbonaceous reducing agents are mixed and fed into the system in specific proportions, with coal constituting the majority of the mixture. Generally, caking coal with high resistivity, suitable caking index, and low graphitization resistance is used as the coal-based reducing agent. Statistics show that while my country has abundant overall coal reserves, the amount of high-quality coal suitable for industrial silicon smelting is relatively small, leading to increased costs associated with its use. Furthermore, the existing low-rank, non-caking whole coal, which constitutes a large proportion of the total coal reserves, has extremely low utilization rates for direct silicon smelting due to its low resistivity and poor caking properties. Therefore, it is essential to comprehensively utilize the existing low-cost, non-caking whole coal with limited industrial value to better reduce excessive production costs caused by raw material usage.

[0004] Coffee shells, as a type of waste biomass, contain abundant organic components such as cellulose, lignin, and hemicellulose. In recent years, the amount of waste coffee shells has been increasing. In order to alleviate the problem of excessive ecological and environmental pressure caused by the large accumulation of waste coffee shells, coffee shell waste is used for efficient, green, and clean production, thereby achieving the goal of recycling and reusing waste resources. Summary of the Invention

[0005] To address the problem of "resource idleness" caused by the large proportion of low-rank coal and its low direct industrial utilization value, this invention proposes a method for preparing composite reducing agent pellets for silicon smelting using all-coal high-value processing. The method involves soaking and activating waste coffee shell powder with NaOH solution to modify the internal organic structure of the powder, enhancing its viscosity and preparing a coffee shell binder. This binder is then used to bind whole coal powder, microsilica powder, and silica powder to prepare composite reducing agent pellets for silicon smelting. The pellets have a strength of 9-13 MPa, meeting the needs of industrial silicon production. After industrial-scale testing, the pellets can achieve a silicon yield of 40-70 t / d, with an energy consumption of 10500-12000 KW·h / t and a carbon excess coefficient of 1.1-1.7.

[0006] A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0007] (1) The vacuum-dried whole coal is crushed and ground to a particle size of less than 0.2 mm to obtain whole coal powder;

[0008] (2) The coffee shell powder was soaked and activated in NaOH solution, and the solid and liquid were separated to obtain the coffee shell binder;

[0009] (3) Grind and mix the whole coal powder, coffee shell binder, micro silica powder and silica powder to obtain a coal powder mixture;

[0010] (4) The coal powder mixture is pressed into a cylindrical blank;

[0011] (5) The cylindrical billet is placed in an argon atmosphere for microwave roasting and then cooled to room temperature in the furnace to obtain composite reducing agent pellets for silicon smelting.

[0012] In step (2), the particle size of the coffee shell powder is less than 0.15 mm.

[0013] In step (2), the mass concentration of the NaOH solution is 4-8%, and the soaking and activation treatment time is 20-60 min.

[0014] In step (3), the particle size of both the microsilica powder and the silica powder is less than 0.15 mm. The SiO2 content in the microsilica powder is 85.2~88.4 wt.%, and the SiO2 content in the silica powder is 99.2~99.8 wt.%.

[0015] In terms of mass percentage, the coal powder mixture in step (3) contains 76-88% whole coal powder, 3-8% coffee shell binder, 8-12% microsilica powder, and 1-4% silica powder.

[0016] The pressing pressure in step (4) is 10~20MPa, the diameter of the cylindrical blank is 60~120mm, and the height is 60~120mm.

[0017] In step (4), the microwave roasting temperature is 450~600℃, the time is 1~3h, and the microwave power is 1~5kW.

[0018] The strength of the composite reducing agent pellets used in step (4) of silicon smelting is 9~13MPa.

[0019] The principle behind this invention for preparing composite reducing agent pellets for silicon smelting is as follows: Coffee shells, a type of waste biomass rich in organic components such as cellulose, lignin, and hemicellulose, are soaked in an appropriate amount of NaOH solution. The -OH groups penetrate into the crystalline regions of the coffee shell fibers, weakening the hydrogen bonds between cellulose and hemicellulose, as well as the saponification of ester bonds between xylan, hemicellulose, and other components. This causes the organic components to swell, increasing porosity and forming a hydrogel with a certain degree of viscosity. Simultaneously, the coffee shells contain a relatively considerable amount of alkali metals, which effectively enhances the reactivity of the pellets in silicon smelting. Accelerating the reaction rate; when coffee shells treated with NaOH solution are used as a binder in the preparation of reducing agent pellets, alkali metal ions will further migrate into the increased pores due to the swelling of organic components, resulting in a relatively uniform distribution of alkali metals in the pellets; the reasonable particle size distribution of microsilica powder can reduce and eliminate precipitation, stratification, and internal stress in the pellets, preventing cracking and enhancing the compressive strength and wear resistance of the prepared pellets; in addition, due to the excellent electrical insulation properties of microsilica powder, adding an appropriate amount of microsilica powder during the pellet preparation process can improve the specific resistivity of the product, further enhancing the utilization efficiency of the pellets.

[0020] The beneficial effects of this invention are:

[0021] (1) In this invention, waste coffee shell powder is soaked and activated by NaOH solution, which modifies the internal organic structure of the coffee shell powder and enhances the viscosity of the coffee shell powder. Coffee shell binder is prepared, and the coffee shell binder is used to bind whole coal powder, microsilica powder and silica powder to prepare composite reducing agent pellets for silicon smelting. The pellets have a strength of 9~13MPa, which meets the needs of industrial silicon production.

[0022] (2) In the process of preparing composite reducing agent pellets for silicon smelting, the present invention adds an appropriate amount of microsilica powder by-products generated by industrial silicon smelting, which further improves the compressive strength and wear resistance of the pellets. At the same time, the presence of microsilica powder during the smelting process increases the resistivity of the pellets and improves the utilization rate of fixed carbon, thereby effectively improving smelting efficiency and reducing production costs.

[0023] (3) After the industrial-scale test of the composite reducing agent pellets for silicon smelting, the silicon production can reach 40~70t / d, the power consumption is 10500~12000KW·h / t, and the carbon excess coefficient is 1.1~1.7. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0025] Example 1: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0026] (1) The whole coal that has been vacuum dried (vacuum dried at 110℃ for 12h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0027] (2) The coffee shell powder (particle size less than 0.15 mm) was added to a 6 wt.% NaOH solution and soaked for 30 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0028] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 76% whole coal powder, 8% coffee shell binder, 12% microsilica powder and 4% silica powder;

[0029] (4) The coal powder mixture was pressed under 10MPa pressure to obtain a cylindrical blank with a diameter of 60mm and a height of 110mm;

[0030] (5) The cylindrical billet was placed in an argon atmosphere (argon flow rate of 1.5L / min) for microwave calcination and cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave calcination temperature was 450℃, the time was 1.5h, and the microwave power was 3kW.

[0031] In this embodiment, the composite reducing agent pellets used in silicon smelting have a strength of 10 MPa. After being used in industrial silicon smelting, they can increase silicon production to 50 t / d, with an energy consumption of 11000 KW·h / t and a carbon excess coefficient of 1.3.

[0032] Example 2: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0033] (1) The whole coal that has been vacuum dried (vacuum dried at 110℃ for 24h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0034] (2) The coffee shell powder (particle size less than 0.15 mm) was added to a 4 wt.% NaOH solution and soaked for 50 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0035] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 88% whole coal powder, 3% coffee shell binder, 8% microsilica powder and 1% silica powder;

[0036] (4) The coal powder mixture was pressed at 15MPa to obtain a cylindrical blank with a diameter of 70mm and a height of 120mm;

[0037] (5) The cylindrical billet is placed in an argon atmosphere (argon flow rate is 1L / min) for microwave roasting, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave roasting temperature is 600℃, the time is 1h, and the microwave power is 2kW.

[0038] In this embodiment, the composite reducing agent pellets used in silicon smelting have a strength of 9 MPa. After being used in industrial silicon smelting, they can achieve a silicon output of 70 t / d, an energy consumption of 10500 KW·h / t, and a carbon excess coefficient of 1.5.

[0039] Example 3: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0040] (1) The whole coal that has been vacuum dried (vacuum dried at 120℃ for 15h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0041] (2) The coffee shell powder (particle size less than 0.15 mm) was added to an 8 wt.% NaOH solution and soaked for 20 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0042] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 80% whole coal powder, 5% coffee shell binder, 11% microsilica powder and 4% silica powder;

[0043] (4) The coal powder mixture is pressed under a pressure of 20MPa to obtain a cylindrical blank with a diameter of 100mm and a height of 60mm;

[0044] (5) The cylindrical billet was placed in an argon atmosphere (argon flow rate of 2L / min) for microwave calcination and cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave calcination temperature was 500℃, the time was 3h, and the microwave power was 1kW.

[0045] In this embodiment, the composite reducing agent pellets used in silicon smelting have a strength of 11 MPa. After being used in industrial silicon smelting, they can achieve a silicon output of 40 t / d, an energy consumption of 12000 KW·h / t, and a carbon excess coefficient of 1.1.

[0046] Example 4: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0047] (1) The whole coal that has been vacuum dried (vacuum dried at 115℃ for 20h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0048] (2) The coffee shell powder (particle size less than 0.15 mm) was added to a 5 wt.% NaOH solution and soaked for 40 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0049] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 85% whole coal powder, 3% coffee shell binder, 9% microsilica powder and 3% silica powder;

[0050] (4) The coal powder mixture was pressed under 12MPa pressure to obtain a cylindrical blank with a diameter of 120mm and a height of 70mm;

[0051] (5) The cylindrical billet was placed in an argon atmosphere (argon flow rate of 1.2L / min) for microwave calcination and cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave calcination temperature was 650℃, the time was 2h, and the microwave power was 4kW.

[0052] In this embodiment, the composite reducing agent pellets used in silicon smelting have a strength of 13 MPa. After being used in industrial silicon smelting, they can achieve a silicon output of 60 t / d, an energy consumption of 11500 KW·h / t, and a carbon excess coefficient of 1.7.

[0053] Example 5: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0054] (1) The whole coal that has been vacuum dried (vacuum dried at 105℃ for 18h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0055] (2) The coffee shell powder (particle size less than 0.15 mm) was added to a 7 wt.% NaOH solution and soaked for 60 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0056] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 79% whole coal powder, 7% coffee shell binder, 10% microsilica powder and 4% silica powder;

[0057] (4) The coal powder mixture is pressed at 18MPa to obtain a cylindrical blank with a diameter of 90mm and a height of 90mm;

[0058] (5) The cylindrical billet was placed in an argon atmosphere (argon flow rate of 1.4 L / min) for microwave calcination and cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave calcination temperature was 480℃, the time was 1h, and the microwave power was 5kW.

[0059] In this embodiment, the composite reducing agent pellet strength for silicon smelting is 12 MPa. After being used in industrial silicon smelting, it can enable silicon production to reach 55 t / d, with an energy consumption of 11200 KW·h / t and a carbon excess coefficient of 1.6.

[0060] Example 6: A method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of all coal, the specific steps of which are as follows:

[0061] (1) The whole coal that has been vacuum dried (vacuum dried at 100℃ for 20h) is crushed and ground to a particle size of less than 0.2mm to obtain whole coal powder;

[0062] (2) The coffee shell powder (particle size less than 0.15 mm) was added to a 6 wt.% NaOH solution and soaked for 40 min to activate it. The solid and liquid were separated to obtain the coffee shell binder.

[0063] (3) Grind and mix whole coal powder, coffee shell binder, microsilica powder and silica powder until they are clearly bonded into lumps to obtain a coal powder mixture; by mass percentage, the coal powder mixture contains 82% whole coal powder, 6% coffee shell binder, 10% microsilica powder and 2% silica powder;

[0064] (4) The coal powder mixture was pressed at 16MPa to obtain a cylindrical blank with a diameter of 110mm and a height of 80mm;

[0065] (5) The cylindrical billet was placed in an argon atmosphere (argon flow rate of 1L / min) for microwave calcination and cooled to room temperature in the furnace to obtain composite reducing agent pellets for silicon smelting; wherein the microwave calcination temperature was 560℃, the time was 3h, and the microwave power was 2kW.

[0066] In this embodiment, the composite reducing agent pellets used in silicon smelting have a strength of 10 MPa. After being used in industrial silicon smelting, they can achieve a silicon output of 45 t / d, an energy consumption of 11600 KW·h / t, and a carbon excess coefficient of 1.4.

[0067] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing composite reducing agent pellets for silicon smelting using high-value coal extraction, characterized in that, The specific steps are as follows: (1) The vacuum-dried whole coal is crushed and ground to a particle size of less than 0.2 mm to obtain whole coal powder; (2) Coffee shell powder is added to NaOH solution for soaking and activation treatment, and solid-liquid separation is performed to obtain coffee shell binder; the mass concentration of the NaOH solution is 4~8%, and the soaking and activation treatment time is 20~60 min; (3) The whole coal powder, coffee shell binder, microsilica powder and silica powder are ground and mixed to obtain a coal powder mixture; the microsilica powder and silica powder The particle size is less than 0.15 mm, the SiO2 content in the microsilica powder is 85.2~88.4 wt.%, and the SiO2 content in the silica powder is 99.2~99.8 wt.%; (4) The coal powder mixture is pressed into a cylindrical blank; (5) The cylindrical blank is placed in an argon atmosphere for microwave roasting, and cooled to room temperature with the furnace to obtain composite reducing agent pellets for silicon smelting; the microwave roasting temperature is 450~600℃, the time is 1~3h, and the microwave power is 1~5kW.

2. The method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of whole coal according to claim 1, characterized in that: Step (2) The particle size of the coffee shell powder is less than 0.15 mm.

3. The method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of whole coal according to claim 1, characterized in that: In terms of mass percentage, the coal powder mixture in step (3) contains 76-88% whole coal powder, 3-8% coffee shell binder, 8-12% microsilica powder, and 1-4% silica powder.

4. The method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of whole coal according to claim 1, characterized in that: Step (4) The pressing pressure is 10~20MPa, the diameter of the cylindrical blank is 60~120mm, and the height is 60~120mm.

5. The method for preparing composite reducing agent pellets for silicon smelting by high-value utilization of whole coal according to claim 1, characterized in that: Step (4) The strength of the composite reducing agent pellets used in silicon smelting is 9~13MPa.