CN102190300A - Method for comprehensive utilization of coal gangue - Google Patents

Abstract

The invention relates to a comprehensive utilization method of coal gangue, which comprises the steps of pulverizing coal gangue-pyrolysis activation-acid dissolution-supplementing carbon source with filter residue-compression molding-high temperature reaction-crushing to obtain silicon carbide. The comprehensive preparation of polyaluminium chloride and photovoltaic cutting edge material-silicon carbide micropowder by utilizing coal gangue in the present invention is an important way for effective comprehensive utilization of coal gangue.

Description

A method for comprehensive utilization of coal gangue

technical field

The invention belongs to the technical field of coal gangue recovery and utilization, and in particular relates to a method for comprehensive utilization of coal gangue.

Background technique

my country has abundant coal resources, and coal gangue is discarded as waste, which not only wastes a lot of resources, occupies a lot of land, but also seriously pollutes the environment. At present, there is a domestic method of preparing polyaluminum chloride from coal gangue, but the remaining slag has not been recycled, and there is still a waste of resources.

For a long time, industrial synthesis of SiC has been using petroleum coke and high-quality silica as the main raw materials. In the late 1980s, SiC was synthesized from anthracite and low-modified bituminous coal, and wastes with Si as the main component, such as coal gangue and natural rice husk, were used to synthesize SiC to reduce costs. However, due to defects in the preparation process, the quality of silicon carbide synthesized from various wastes is not high, and the purity is generally below 90%, so it cannot be used as a photovoltaic cutting edge.

Contents of the invention

The object of the present invention is to provide a comprehensive utilization method of coal gangue.

The present invention adopts following technical scheme:

A method for comprehensive utilization of coal gangue, the steps of which are:

(1) Crush the gangue to a particle size below 0.1mm;

(2) Pyrolyze and activate the pulverized material at 600-800°C for 0.5-1h;

(3) The activated material is pulverized to less than 100 μm, and dissolved in hydrochloric acid for 1-4 hours under normal pressure of 100-110°C or 0.4-0.5MPa at a temperature of 140-150°C, and the solid-to-liquid mass ratio is 1:4;

(4) Solid-liquid separation;

(5) Supplementing the carbon source to the filter residue obtained by solid-liquid separation, so that the molar ratio of C and _SiO2 in it is 3.5-4.5;

(6) Grind the obtained material to a particle size of less than 100 μm, press and shape it at 5-10 MPa, and react at 1350-1500 °C for 4-6 hours under the protection of an inert gas;

(7) Lower the temperature to 700-850°C, turn off the inert gas, let in air, and cool naturally to obtain silicon carbide.

The heating rate in the step (6) is 5°C/min.

Crush the silicon carbide obtained in step (7) to 1000-2000 mesh; add water and flotation agent, stir and then stand for flotation; continue to add sulfuric acid or hydrochloric acid and hydrofluoric acid to pickle and remove impurities; the solid obtained by solid-liquid separation is dried After classification, silicon carbide micropowders with different particle sizes are obtained.

The amount of water used is 1-1.5 times the mass of silicon carbide, and the amount of flotation agent is 1-5‰ of the mass of silicon carbide.

The amount of hydrochloric acid or sulfuric acid is 5-20% of the mass of silicon carbide, and the amount of hydrofluoric acid is 5-15% of the mass of silicon carbide.

The flotation agent is kerosene, water glass or detergent.

The filtrate is ripened, hydrolyzed and polymerized to prepare polyaluminum chloride.

Compared with the prior art, the present invention has the following beneficial effects: the present invention utilizes coal gangue to obtain three kinds of industrial products: polyaluminum chloride, silicon carbide (more than 95% content) and photovoltaic cutting edge material-silicon carbide micropowder (more than 97% content). In the process of activating and roasting coal gangue, the organic matter in it is effectively used, which reduces the influence of carbon in coal gangue on the quality of aluminum chloride extracted; through the preparation of polyaluminum chloride, the aluminum resources in coal gangue are effectively used, and at the same time it is equivalent to coal The silicon dioxide in the gangue has been effectively removed; the process of flotation after grinding and then pickling has been cleverly used to increase the purity of the prepared silicon carbide from 95% to more than 97% of the silicon carbide powder, thereby obtaining quality Qualified photovoltaic cutting edge material - silicon carbide powder. Therefore, the comprehensive preparation of polyaluminum chloride and photovoltaic cutting edge material-silicon carbide micropowder by using coal gangue is an important way for the effective comprehensive utilization of coal gangue.

Description of drawings

Fig. 1 is the scanning electron micrograph of the 1000 order silicon carbide micro-powders of embodiment 1 classification gained;

Fig. 2 is the scanning electron micrograph of the 1200 order silicon carbide micro-powders of embodiment 1 classification gained;

Fig. 3 is the scanning electron micrograph of the 1500 order silicon carbide micro-powders of classification gained in embodiment 2;

Fig. 4 is the scanning electron micrograph of the 1800 order silicon carbide micropowders of embodiment 3 classification gained;

5 is a scanning electron microscope image of the 2000-mesh silicon carbide micropowder with many grades in Example 2.

Detailed ways

Example 1

The steps of preparing polyaluminum chloride:

(1) Crush and finely grind the gangue to 0.10mm;

(2) Put the pulverized coal gangue powder in a high-temperature tube furnace, and activate it by pyrolysis at 600°C for 1 hour. A small amount of organic matter in the gangue can not only act as part of the heat source, but also reduce the impact of carbon in the gangue on the extraction of chlorine. The influence of the quality of aluminum;

(3) The activated coal gangue powder is acid-dissolved with hydrochloric acid at 100°C for 4 hours, the mass ratio of solid to liquid is 1:4, the aluminum in the powder is dissolved in the acid in the form of aluminum chloride, and other traces of iron, calcium, magnesium, etc. The oxide also enters the solution in the form of chloride, and the leaching rate of aluminum chloride is over 90%;

(4) After solid-liquid separation, the filtrate is matured, hydrolyzed and polymerized, and the basicity is adjusted with calcium aluminate or sodium aluminate to prepare the water treatment agent polyaluminum chloride. The aluminum oxide content in the liquid polyaluminum chloride is 13.2%, and the salt The base rate is 46.8%. A small amount of calcium, iron, magnesium, and silicon contained in it have no side effects on its flocculation performance, because iron oxide, calcium oxide, magnesium oxide, etc. have good flocculation effects;

Steps for preparing silicon carbide micropowder:

(5) The main component of the filter residue obtained in step (4) is SiO ₂ , and the carbon source is supplemented through analysis and calculation, so that the molar ratio of C to SiO ₂ is 3.5;

(6) Ball mill the prepared material to less than 100 μm, press it under 5 MPa pressure, put it into a high-temperature furnace, under the protection of argon, the argon flow rate is 1mL/s, the heating rate is 5°C/min, and react at 1350°C for 3h ;

(7) Cool down to 700 °C, turn off the argon gas, let in air, and cool naturally to produce silicon carbide with a purity of 95.0%;

(8) Grinding and ball milling the prepared silicon carbide to 1000-2000 mesh;

(9) Add water with 1 times the mass of silicon carbide, add kerosene with 1‰ mass of silicon carbide, mechanically stir, stand still and flotation to remove excess carbon as a carbon source for reuse, then add sulfuric acid with 5% mass of silicon carbide, 5‰ Hydrofluoric acid pickling and impurity removal;

(10) The silicon carbide micropowder washed with pure water is dried by a spray dryer;

(11) The dried micropowder is graded to obtain photovoltaic cutting edge material-silicon carbide micropowder that meets the requirements of particle size requirements of 1000 mesh, 1200 mesh, 1500 mesh, 1800 mesh and 2000 mesh, and the purity of silicon carbide in the micropowder is 97.2%.

The scanning electron microscope images of 1000-mesh and 1200-mesh photovoltaic cutting edge material-silicon carbide powder obtained by classification are shown in Figure 1 and Figure 2 respectively. It can be seen from the figure that the particle size of silicon carbide powder is uniform and sharp.

Example 2

The steps of preparing polyaluminum chloride:

(1) Crush and finely grind the gangue to 0.08mm;

(2) Put the pulverized coal gangue powder in a fluidized fluidized furnace, and activate it by pyrolysis at 650°C for 0.8 hours; a small amount of organic matter in the gangue can not only act as part of the heat source, but also reduce the impact of carbon in the gangue on the quality of aluminum chloride extracted Impact;

(3) The activated gangue powder is dissolved in hydrochloric acid at 0.4MPa and 145°C for 3 hours, the mass ratio of solid to liquid is 1:4, the aluminum in the powder is dissolved in the acid in the form of aluminum chloride, other trace iron, Oxides such as calcium and magnesium also enter the solution in the form of chloride, and the leaching rate of aluminum chloride is over 90%;

(4) After solid-liquid separation, the filtrate is matured, hydrolyzed and polymerized, and the basicity is adjusted with calcium aluminate or sodium aluminate to prepare the water treatment agent polyaluminum chloride. The aluminum oxide content in the liquid polyaluminum chloride is 13.6%, and the salt The base rate is 50.2%. A small amount of calcium, iron, magnesium, and silicon contained in it have no side effects on its flocculation performance, because iron oxide, calcium oxide, magnesium oxide, etc. have good flocculation effects;

Steps for preparing silicon carbide micropowder:

(5) The main component of the filter residue obtained in step (4) is SiO ₂ , and the carbon source is supplemented through analysis and calculation, so that the molar ratio of C to SiO ₂ is 4;

(6) Ball mill the prepared material to be less than 80 μm, press it under 8MPa pressure, put it into a high-temperature furnace, and under the protection of argon, the argon flow rate is 1mL/s, the heating rate is 5°C/min, and react at 1400°C for 4h ;

(7) Cool down to 800 °C, turn off the argon gas, let in the air, and cool naturally to produce silicon carbide with a purity of 95.5%;

(8) Grinding and ball milling the prepared silicon carbide to 1000-2000 mesh;

(9) Add water with 1.3 times the mass of silicon carbide, add detergent with a mass of 3‰ of silicon carbide, mechanically stir, stand still and flotation to remove excess carbon as a carbon source for reuse, then add hydrochloric acid with a mass of 10% of silicon carbide and 10‰ hydrofluoric acid pickling to remove impurities;

(10) The silicon carbide micropowder washed with pure water is dried by a spray dryer;

(11) The dried micropowders were classified to obtain photovoltaic cutting edge material-silicon carbide micropowders of 1000 mesh, 1200 mesh, 1500 mesh, 1800 mesh and 2000 mesh, among which the purity of silicon carbide in the micropowder was 97.8%.

The scanning electron microscope images of 1500-mesh and 2000-mesh photovoltaic cutting edge material-silicon carbide powder obtained by classification are shown in Figures 3 and 5 respectively. It can be seen from the figure that the particle size of silicon carbide powder is uniform and sharp.

Example 3

The steps of preparing polyaluminum chloride:

(1) Crush and finely grind the gangue to 0.08mm;

(2) Put the pulverized gangue powder in a high-temperature tube furnace, and activate it by pyrolysis at 800°C for 0.5 hours; a small amount of organic matter in the gangue can not only act as part of the heat source, but also reduce the impact of carbon in the gangue on the extraction of chlorine. The influence of the quality of aluminum;

(3) The activated coal gangue powder is acid-dissolved with hydrochloric acid at 110°C for 1 hour, the mass ratio of solid to liquid is 1:4, the aluminum in the powder is dissolved in the acid in the form of aluminum chloride, and other traces of iron, calcium, magnesium, etc. The oxide also enters the solution in the form of chloride, and the leaching rate of aluminum chloride is over 90%;

(4) After solid-liquid separation, the filtrate is matured, hydrolyzed and polymerized, and the basicity is adjusted with calcium aluminate or sodium aluminate to prepare the water treatment agent polyaluminum chloride. The aluminum oxide content in the liquid polyaluminium chloride is 14.0%, and the salt The base rate is 55.0%. A small amount of calcium, iron, magnesium, and silicon contained in it have no side effects on its flocculation performance, because iron oxide, calcium oxide, magnesium oxide, etc. have good flocculation effects;

Steps for preparing silicon carbide micropowder:

(5) The main component of the filter residue obtained in step (4) is SiO ₂ , and the carbon source is supplemented through analysis and calculation, so that the molar ratio of C to SiO ₂ is 4.5;

(6) Ball mill the prepared material to below 80 μm, press it under 10MPa pressure, put it into a high-temperature furnace, and under the protection of argon, the flow rate of argon gas is 1mL/s, and the heating rate is 5°C/min. Reaction 6h;

(7) Cool down to 700~850°C, turn off the argon gas, turn off the power supply, let in air, and cool naturally to produce silicon carbide with a purity of 95.9%;

(8) Grinding and ball milling the prepared silicon carbide to 1000-2000 mesh;

(9) Add water with 1.5 times the mass of silicon carbide, add water glass with 5‰ mass of silicon carbide, mechanically stir, stand still and flotation to remove excess carbon as a carbon source for reuse, then add hydrochloric acid with 20% mass of silicon carbide and 15 ‰ hydrofluoric acid pickling to remove impurities;

(10) The silicon carbide micropowder washed with pure water is dried by a spray dryer;

(11) The dried micropowders were classified to obtain photovoltaic cutting edge material-silicon carbide micropowders of 1000 mesh, 1200 mesh, 1500 mesh, 1800 mesh and 2000 mesh, among which the purity of silicon carbide in the micropowder was 98.2%.

The scanning electron microscope image of the 1800-mesh photovoltaic cutting edge material-silicon carbide powder obtained by classification is shown in Figure 4. It can be seen from the figure that the particle size of the silicon carbide powder is uniform and sharp.

Claims (7)

1. a coal gangue method of comprehensive utilization the steps include:

(1) colliery powder is broken to below the particle diameter 0.1mm;

(2) material after will pulverizing is in 600-800 ℃ of following pyrolysis activation 0.5-1h;

(3) material after the activation is crushed to below the 100 μ m, normal pressure 100-110 ℃ down or the 0.4-0.5MPa temperature be 140-150 ℃ down with the molten 1-4h of hydrochloric acid acid, the solid-liquid mass ratio is 1:4;

(4) solid-liquid separation;

(5) supplementary carbon source in solid-liquid separation gained filter residue makes wherein C and SiO ₂Mol ratio to 3.5-4.5;

(6) the gained material is milled to below the particle diameter 100 μ m, compression moulding under 5-10MPa is reacted 4-6h in 1350-1500 ℃ under protection of inert gas;

(7) be cooled to 700-850 ℃, turn off rare gas element, bubbling air, naturally cooling gets silicon carbide.

2. coal gangue method of comprehensive utilization as claimed in claim 1 is characterized in that: heat-up rate is 5 ℃/min in the described step (6).

3. coal gangue method of comprehensive utilization as claimed in claim 1 or 2 is characterized in that: step (7) gained carborundum powder is broken to the 1000-2000 order; Add entry and flotation agent, leave standstill flotation after the stirring; Continue to add sulfuric acid or hydrochloric acid and hydrofluoric acid pickling impurity removal; Solid-liquid separation gained solid classification after drying obtains varigrained silicon carbide micro-powder.

4. coal gangue method of comprehensive utilization as claimed in claim 3 is characterized in that: the consumption of described water is 1-1.5 a times of silicon carbide quality, and the consumption of flotation agent is the 1-5 ‰ of silicon carbide quality.

5. coal gangue method of comprehensive utilization as claimed in claim 4 is characterized in that: described hydrochloric acid or vitriolic consumption are the 5-20% of silicon carbide quality, and the consumption of described hydrofluoric acid is the 5-15 ‰ of silicon carbide quality.

6. coal gangue method of comprehensive utilization as claimed in claim 5 is characterized in that: described flotation agent is kerosene, water glass or liquid detergent.

7. coal gangue method of comprehensive utilization as claimed in claim 1 is characterized in that: described filtrate prepares polymerize aluminum chloride through slaking, hydrolysis and polymerization.

Images