A method for removing silicon from biomass capacitive carbon

Abstract

The invention relates to the technical field of activated carbon, and discloses a method for removing silicon from biomass capacitor carbon, comprising the following steps: introducing a gas phase cleaning agent at 50-80°C into biomass capacitor carbon particles to be desiliconized at room temperature for desiliconization, with an air flow rate of 0.1-2 L / min and a reaction time of 0.5-3h; the moisture content of the biomass capacitor carbon particles to be desiliconized is ≤500 ppm; the gas phase cleaning agent is 97-99% N 2 and 1‑3% COF 2 Alternatively, the gas phase cleaning agent is 95-98% N 2 , 1‑3% COF 2 The present invention adopts a gas phase cleaning agent containing carbonyl fluoride, which can quickly enter the pores of activated carbon, react with silicon-containing impurities to generate volatile products and then discharge them, with high impurity removal rate, simple process and no need for waste liquid post-treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of activated carbon, and in particular to a method for removing silicon from biomass capacitive carbon. Background Art

[0002] Biomass supercapacitor activated carbon usually contains a certain amount of silicon impurities such as silicon oxides and silicates. For supercapacitors using organic electrolytes, silicon impurities will not only cause leakage current, reduce the actual working voltage, increase the internal resistance, but also trigger side reactions such as the decomposition of the electrolyte, deteriorating the cycle performance of the supercapacitor. Therefore, in practical applications, it is necessary to remove inorganic silicon impurities in biomass supercapacitor activated carbon, and usually an acid cleaning solution containing hydrofluoric acid is used for removal. For example, the invention patent with the publication number CN111732101A discloses a preparation method of coal-based supercapacitor activated carbon, including: S1, selecting coal with an ash content of less than 5% as the raw coal; S2, carbonizing and activating the raw coal to obtain primary activated carbon with a specific surface area of 500-1000m 2 / g; S3, grinding the primary activated carbon to less than 100 mesh, then soaking it in hydrofluoric acid and washing it to neutral; S4, performing a heating treatment under the protection of an inert gas; S5, reacting the material obtained by the heating treatment in step S4 with potassium hydroxide according to a mass ratio of 1:(1-6); S6, washing the obtained reactant to neutral, which is the coal-based supercapacitor activated carbon.

[0003] However, since most of the pores in biomass supercapacitor activated carbon are micropores and mesopores with a pore diameter of less than 5 nm, the pore structure and surface state are complex and changeable. When removing inorganic impurities in activated carbon by acid washing, the acid cleaning solution diffuses slowly into the deep parts of the micropores and mesopores and is not easy to reach the deepest part, resulting in low silicon removal efficiency, time-consuming cleaning process, and unstable purity of the activated carbon, which cannot meet the requirements of high-performance organic supercapacitors. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for removing silicon from biomass capacitive carbon, changing the liquid-phase cleaning to gas-phase cleaning, so that the gas-phase cleaning agent with high diffusivity and high permeability can quickly enter the porous structure of the activated carbon and reach the deep part, react with the silicon-containing impurities and generate volatile products and then be discharged, thereby effectively removing silicon-containing impurities such as silicon dioxide inside the porous structure of the biomass activated carbon.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] The present invention provides a method for removing silicon from biomass capacitive carbon, comprising the following steps: introducing a gaseous cleaning agent at 50 - 80 °C into the silicon-removing biomass capacitive carbon particles at room temperature for silicon removal, with an air flow rate of 0.1 - 2 L / min and a reaction time of 0.5 - 3 h; the water content of the silicon-removing biomass capacitive carbon particles ≤ 500 ppm; by volume percentage, the gaseous cleaning agent is 97 - 99% of N 2 and 1 - 3% of COF 2 , or, the gaseous cleaning agent is 95 - 98% of N 2 、1 - 3% of COF 2 and 1 - 2% of HF.

[0007] When removing inorganic silicon impurities from biomass supercapacitor activated carbon in the prior art, an acid cleaning solution containing hydrofluoric acid is usually used for removal. However, since the acid cleaning solution diffuses relatively slowly into the deep pores of micropores and mesopores and is not easily reach the deepest part, the silicon removal efficiency is low, and the post-treatment process of acid cleaning is relatively complex, resulting in a time-consuming cleaning process. Therefore, the present invention uses a gaseous cleaning agent for silicon removal, that is, changing the liquid-phase cleaning to gaseous cleaning. Using a gaseous cleaning agent containing carbonyl fluoride (COF 2 ), on the one hand, the HF generated by the reaction of carbonyl fluoride with water reacts with silicon dioxide impurities to achieve the silicon removal effect, and on the other hand, the introduction of carbonyl fluoride and HF together can further improve the silicon removal efficiency. At the same time, N 2 in the gaseous cleaning agent can be used as a carrier gas to better assist COF 2 and HF to enter the mesopores and micropores of activated carbon for silicon removal. And there is a certain temperature difference between the introduced gaseous cleaning agent and the activated carbon. Introducing it at an appropriate temperature can not only ensure the safety of the reaction, but also help HF and the generated H 2 O to form an acid mist, improving the wettability of HF for silicon removal, and thus improving the silicon removal efficiency.

[0008] The chemical equations for the silicon removal reaction by the gaseous cleaning agent are as follows:

[0009] COF 2 +H 2 O = CO 2 ↑ + 2HF↑

[0010] SiO 2 + 4HF = SiF 4 ↑ + 2H 2 O

[0011] As a preference, when the water content of the silicon-removing biomass capacitive carbon particles > 200 ppm, by volume percentage, the gaseous cleaning agent is 97 - 99% of N 2 and 1 - 3% of COF 2. When the moisture content of the silicon-removing biomass capacitive carbon particles ≤ 200 ppm, by volume percentage, the gas-phase cleaning agent is 95 - 98% of N 2 , 1 - 3% of COF 2 and 1 - 2% of HF.

[0012] To further improve the silicon-removing efficiency and reduce costs, when the moisture content of the biomass capacitive carbon to be desilicified > 200 ppm, the gas-phase cleaning agent may not contain HF gas. This is because when the moisture content is relatively high, COF 2 can react quickly and fully with the water in the biomass capacitive carbon to generate HF gas, and the generated HF gas is sufficient to react fully with the silicon dioxide impurities, thus achieving a good silicon-removing effect. When the moisture content of the biomass capacitive carbon to be desilicified ≤ 200 ppm, the HF gas contained in the gas-phase cleaning agent can react with the silicon dioxide impurities to generate SiF 4 gas and H 2 O. Since the original moisture content in the biomass capacitive carbon is relatively low, the generated H 2 O is more likely to react with COF 2 to further generate HF, thereby enabling a more efficient silicon-removing reaction.

[0013] Preferably, the silicon content of the silicon-removing biomass capacitive carbon particles ≤ 500 ppm.

[0014] Preferably, the total content of calcium and magnesium impurity elements contained in the silicon-removing biomass capacitive carbon particles < 20 ppm.

[0015] Preferably, the silicon-removing biomass capacitive carbon particles are dried by hot air at 50 - 80 °C to reduce the moisture content.

[0016] Preferably, the gas flow rate during silicon removal is 0.2 - 1 L / min, and the reaction time is 1 - 2 h.

[0017] Preferably, the silicon-removing biomass capacitive carbon particles are stacked to form a fixed bed layer.

[0018] Preferably, after silicon removal, it is cooled, and the residual gas in the biomass capacitive carbon particles is replaced with nitrogen.

[0019] Preferably, the residual gas includes one or more of COF 2 , HF, CO 2 and SiF 4 .

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Use a gas-phase cleaning agent containing carbonyl fluoride. On the one hand, the HF generated by the reaction of carbonyl fluoride with water reacts with silicon dioxide impurities to achieve the effect of silicon removal. On the other hand, introducing carbonyl fluoride and HF together can further improve the silicon removal efficiency;

[0022] (2) The N in the gas-phase cleaning agent 2 can be used as a carrier gas to better assist COF 2 and HF to enter the mesopores and micropores of activated carbon for silicon removal;

[0023] (3) There is a certain temperature difference between the introduced gas-phase cleaning agent and the activated carbon. Introducing it at an appropriate temperature can not only ensure the safety of the reaction, but also help HF react with the generated H 2 O to form acid mist, improve the wettability of HF for silicon removal, and thus improve the silicon removal efficiency;

[0024] (4) The gas-phase cleaning agent with high diffusivity and high permeability can quickly enter the pores of activated carbon, react with silicon-containing impurities, generate volatile products and then be discharged. The impurity removal rate is high, the process is simple, and no post-treatment of waste liquid is required. Specific Embodiments

[0025] The following specific examples are used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto.

[0026] The method for removing silicon from biomass capacitive carbon in the present invention includes the following steps:

[0027] (1) In a tank lined with PTFE, fill the biomass capacitive carbon particles to be desilicified to form a continuous fixed bed layer. The silicon content of the biomass capacitive carbon particles to be desilicified is ≤500 ppm, and the total content of calcium and magnesium impurity elements is <20 ppm (to avoid the reaction of calcium and magnesium impurity elements with HF to form insoluble solid impurities such as calcium fluoride and magnesium fluoride).

[0028] (2) Introduce dry air at 50 - 80 °C into the tank and flow it through the fixed bed layer to perform dry pretreatment on the biomass capacitive carbon particles filled in the fixed bed layer, so that the moisture content of the biomass capacitive carbon particles to be desilicified is ≤500 ppm. After the dry pretreatment, the biomass capacitive carbon particles to be desilicified need to be cooled to room temperature to prevent the heat release caused by the reaction of COF 2 in the gas-phase cleaning agent with moisture and surface functional groups of activated carbon, and avoid the safety problems that are likely to occur after overheating.

[0029] (3) At room temperature, introduce a gas-phase cleaning agent at 50 - 80 °C into the tank and flow it through the fixed bed layer to remove silicon from the biomass capacitive carbon particles filled in the fixed bed layer. By volume percentage, the gas-phase cleaning agent is 97 - 99% N 2 and 1 - 3% COF 2, or, the vapor-phase cleaning agent is 95-98% N 2 、1-3% COF 2 and 1-2% HF, the gas flow rate of the vapor-phase cleaning agent is 0.1-2 L / min, and the desiliconization reaction time is 0.5-3 h.

[0030] (4) After the desiliconization reaction, the biomass capacitive carbon particles filled in the fixed bed layer are cooled to room temperature, and then the residual gas in the biomass capacitive carbon particles is replaced with dry high-purity nitrogen. The residual gas includes COF 2 、HF、CO 2 、SiF 4 one or more of them.

[0031] In a specific embodiment of the present invention, the particle size range of the biomass capacitive carbon particles to be desilicified is 0.5-5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2-0.7 g / cm³, and the ash content is 0.1-0.5%.

[0032] In a specific embodiment of the present invention, more preferably, when the moisture content of the biomass capacitive carbon particles to be desilicified > 200 ppm, by volume percentage, the vapor-phase cleaning agent is 90-95% N 2 and 5-10% COF 2 .

[0033] In a specific embodiment of the present invention, the room temperature is 10-30°C.

[0034] Example 1

[0035] (1) In a tank lined with PTFE, fill the biomass capacitive carbon particles to be desilicified to form a continuous fixed bed layer. The moisture content of the biomass capacitive carbon particles to be desilicified is 2-3%, the silicon content is 200-400 ppm, the ash content is 0.1-0.5%, the particle size range is 0.5-5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2-0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0036] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried biomass capacitive carbon particles to be desilicified is 280 ppm.

[0037] (3) After cooling to 25°C room temperature, the 70°C vapor-phase cleaning agent (by volume percentage, the vapor-phase cleaning agent is 97% N 2 、3% COF 2Flow into the tank body and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0038] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then replace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0039] Example 2

[0040] The difference from Example 1 is that the gas flow rate of the gas-phase cleaning agent is 1 L / min, and the silicon-removing reaction time is 0.5 h.

[0041] (1) In the tank body lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0042] (2) Pass 70°C dry air into the tank body and flow through the fixed bed layer to perform dry pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 280 ppm.

[0043] (3) After cooling to room temperature of 25°C, pass a 70°C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 97% N 2 , 3% COF 2 ) into the tank body and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 1 L / min, and the silicon-removing reaction time is 0.5 h.

[0044] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then replace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0045] Example 3

[0046] The difference from Example 1 is that: by volume percentage, the gas-phase cleaning agent is 99% N 2 and 1% COF 2 .

[0047] (1) In a tank lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2-3%, the silicon content is 200-400 ppm, the ash content is 0.1-0.5%, the particle size range is 0.5-5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2-0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0048] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 280 ppm.

[0049] (3) After cooling to room temperature of 25°C, pass a 70°C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 99% N 2 and 1% COF 2 ) into the tank and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passed in is 0.5 L / min, and the silicon removal reaction time is 1 h.

[0050] (4) After the silicon removal reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0051] Example 4

[0052] The difference from Example 1 is that: by volume percentage, the gas-phase cleaning agent is 97% N 2 , 2% COF 2 and 1% HF.

[0053] (1) In a tank lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2-3%, the silicon content is 200-400 ppm, the ash content is 0.1-0.5%, the particle size range is 0.5-5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements is < 20 ppm.

[0054] (2) Pass dry air at 70 °C into the tank body and flow through the fixed bed layer to perform dry pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles after drying is 280 ppm.

[0055] (3) After cooling to room temperature of 25 °C, pass a 70 °C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 97% N 2 、2% COF 2 and 1% HF) into the tank body and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passed in is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0056] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25 °C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 、HF、CO 2 、SiF 4 .

[0057] Example 5

[0058] The difference from Example 1 is that the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm.

[0059] (1) In the tank body lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements is < 20 ppm.

[0060] (2) Pass dry air at 70 °C into the tank body and flow through the fixed bed layer to perform dry pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles after drying is 100 ppm.

[0061] (3) After cooling to room temperature of 25 °C, pass a 70 °C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 97% N 2 、3% COF 2Flow into the tank body and pass through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0062] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then replace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0063] Example 6

[0064] The difference from Example 1 is that the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm; the gas flow rate of the gas-phase cleaning agent is 0.2 L / min, and the silicon-removing reaction time is 2 h.

[0065] (1) In the tank body lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0066] (2) Pass 70°C dry air into the tank body and pass through the fixed bed layer to perform dry pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0067] (3) After cooling to room temperature of 25°C, pass a 70°C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 97% N 2 , 3% COF 2 ) into the tank body and pass through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 0.2 L / min, and the silicon-removing reaction time is 2 h.

[0068] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then replace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0069] Example 7

[0070] The difference from Example 1 is that the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm; by volume percentage, the gas-phase cleaning agent is 98% N 2 and 2% COF 2 .

[0071] (1) In a tank lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0072] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. After drying, the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm.

[0073] (3) After cooling to room temperature of 25°C, pass a 70°C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 98% N 2 、2% COF 2 ) into the tank and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passing in is 0.5 L / min, and the silicon removal reaction time is 1 h.

[0074] (4) After the silicon removal reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 、HF、CO 2 、SiF 4 .

[0075] Example 8

[0076] The difference from Example 1 is that the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm; by volume percentage, the gas-phase cleaning agent is 95% N 2 、3% COF 2 and 2% HF.

[0077] (1) In a PTFE-lined tank, fill with silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0078] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0079] (3) After cooling to room temperature of 25°C, pass a 70°C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 95% N 2 、3% COF 2 and 2% HF) into the tank and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passed in is 0.5 L / min, and the silicon removal reaction time is 1 h.

[0080] (4) After the silicon removal reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 、HF、CO 2 、SiF 4 .

[0081] Example 9

[0082] The difference from Example 1 is that: the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm; by volume percentage, the gas-phase cleaning agent is 97% N 2 、2% COF 2 and 1% HF.

[0083] (1) In a PTFE-lined tank, fill with silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0084] (2) Pass dry air at 70 °C into the tank and flow it through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0085] (3) After cooling to room temperature of 25 °C, pass a 70 °C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 97% N 2 、2% COF 2 and 1% HF) into the tank and flow it through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passed in is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0086] (4) After the silicon-removing reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25 °C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes COF 2 、HF、CO 2 、SiF 4 .

[0087] Example 10

[0088] The difference from Example 1 is that: the moisture content of the silicon-removing biomass capacitive carbon particles is 100 ppm; by volume percentage, the gas-phase cleaning agent is 98% N 2 、1% COF 2 and 1% HF.

[0089] (1) In a tank lined with PTFE, fill silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0090] (2) Pass dry air at 70 °C into the tank and flow it through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0091] (3) After cooling to room temperature of 25 °C, pass a 70 °C gas-phase cleaning agent (by volume percentage, the gas-phase cleaning agent is 98% N 2 、1% COF 2The gas-phase cleaning agent (98% N₂ and 1% HF) is introduced into the tank body and flows through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0092] After the silicon-removing reaction, the biomass capacitive carbon particles filled in the fixed bed layer are cooled to room temperature of 25°C, and then the residual gas in the biomass capacitive carbon particles is replaced with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0093] Comparative Example 1

[0094] The difference from Example 5 is that, by volume percentage, the gas-phase cleaning agent is 100% N 2 .

[0095] (1) In a tank body lined with PTFE, silicon-removing biomass capacitive carbon particles are filled to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area ≥ 1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is < 20 ppm.

[0096] (2) Dry air at 70°C is introduced into the tank body and flows through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0097] After cooling to room temperature of 25°C, the gas-phase cleaning agent at 70°C (by volume percentage, the gas-phase cleaning agent is 100% N 2 ) is introduced into the tank body and flows through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent is 0.5 L / min, and the silicon-removing reaction time is 1 h.

[0098] After the silicon-removing reaction, the biomass capacitive carbon particles filled in the fixed bed layer are cooled to room temperature of 25°C.

[0099] Comparative Example 2

[0100] The difference from Example 7 is that, by volume percentage, the gas-phase cleaning agent is 98% N 2 and 2% HF.

[0101] (1) In a tank lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area is ≥1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is <20 ppm.

[0102] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0103] (3) After cooling to room temperature of 25°C, pass a gas-phase cleaning agent at 70°C (by volume percentage, the gas-phase cleaning agent is 98% N 2 and 2% HF) into the tank and flow through the fixed bed layer to remove silicon from the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the gas-phase cleaning agent passed in is 0.5 L / min, and the silicon removal reaction time is 1 h.

[0104] (4) After the silicon removal reaction, cool the biomass capacitive carbon particles filled in the fixed bed layer to room temperature of 25°C, and then displace the residual gas in the biomass capacitive carbon particles with dry high-purity nitrogen. The residual gas includes HF and SiF 4 .

[0105] Comparative Example 3

[0106] The difference from Example 5 is that a gas-phase cleaning agent at room temperature of 25°C is passed in for silicon removal.

[0107] (1) In a tank lined with PTFE, fill the silicon-removing biomass capacitive carbon particles to form a continuous fixed bed layer. The moisture content of the silicon-removing biomass capacitive carbon particles is 2 - 3%, the silicon content is 200 - 400 ppm, the ash content is 0.1 - 0.5%, the particle size range is 0.5 - 5.0 mm, the specific surface area is ≥1000 m 2 / g, the tapped density is 0.2 - 0.7 g / cm³, and the total content of calcium and magnesium impurity elements contained is <20 ppm.

[0108] (2) Pass dry air at 70°C into the tank and flow through the fixed bed layer to perform a drying pretreatment on the silicon-removing biomass capacitive carbon particles filled in the fixed bed layer. The moisture content of the dried silicon-removing biomass capacitive carbon particles is 100 ppm.

[0109] (3) After cooling to room temperature of 25 °C, a vapor-phase cleaning agent at 25 °C room temperature (by volume percentage, the vapor-phase cleaning agent is 97% N 2 , 3% COF 2 ) is introduced into the tank body and flows through the fixed bed layer to remove silicon from the silicon-containing biomass capacitive carbon particles filled in the fixed bed layer. The gas flow rate of the introduced vapor-phase cleaning agent is 0.5 L / min, and the silicon removal reaction time is 1 h.

[0110] (4) After the silicon removal reaction, the biomass capacitive carbon particles filled in the fixed bed layer are cooled to room temperature of 25 °C, and then the residual gas in the biomass capacitive carbon particles is replaced with dry high-purity nitrogen. The residual gas includes COF 2 , HF, CO 2 , SiF 4 .

[0111] Table 1

[0112]

[0113] As shown in Table 1, comparing Examples 1-10 with Comparative Examples 1-3, the vapor-phase cleaning agent containing COF 2 adopted in the present invention can have an efficient silicon removal effect. For biomass capacitive carbon with a silicon content of 200-400 ppm, its silicon content can be reduced to 50 ppm or less. In Comparative Example 2, only N 2 and HF are used as the vapor-phase cleaning agent. Although it can achieve a certain silicon removal effect compared to Comparative Example 1 using only N 2 as the vapor-phase cleaning agent, its silicon removal effect is worse than that of Example 7. Both use the same volume content of N 2 . Since COF 2 is used for silicon removal in Example 7, the silicon removal reaction efficiency is significantly improved, and thus activated carbon with a lower silicon content can be obtained under the same conditions. Moreover, the introduction temperature of the vapor-phase cleaning agent is also particularly important for the silicon removal effect. In Comparative Example 3, the vapor-phase cleaning agent at room temperature is used for silicon removal, and the silicon content of the final activated carbon is still relatively high.

[0114] In addition, when the present invention uses a vapor-phase cleaning agent containing COF 2 for silicon removal, a larger moisture content of the capacitive carbon is more conducive to obtaining a better silicon removal effect. However, within the range of the silicon removal reaction parameter conditions defined in the present invention, even under the condition of capacitive carbon with a lower moisture content, a better silicon removal effect can still be obtained compared to Comparative Examples 1-3. Comparing Examples 1-3 with Examples 5-7, the vapor-phase cleaning agent containing N 2 and COF 2 is relatively more affected by the water content of the biomass capacitive carbon, but activated carbon with a lower silicon content can be obtained in both cases. Comparing Example 4 with Examples 8-10, the vapor-phase cleaning agent containing N2 , HF, and COF 2 The gas-phase cleaning agents of are less affected by the water content of biomass capacitive carbon. The larger the total volume ratio of COF 2 and HF, the better the silicon removal effect. However, if the total volume ratio of HF and COF 2 is too large, it will be unfavorable for reaction safety.

[0115] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for removing silicon from biomass capacitor carbon, characterized in that: The method comprises the following steps: introducing a gas phase cleaning agent at 50-80° C. into biomass capacitor carbon particles to be desiliconized at room temperature for desiliconization, with an air flow rate of 0.1-2 L / min and a reaction time of 0.5-3 h; the moisture content of the biomass capacitor carbon particles to be desiliconized is ≤500 ppm; and the gas phase cleaning agent is 97-99% N2 and 1-3% COF2, or the gas phase cleaning agent is 95-98% N2, 1-3% COF2 and 1-2% HF, in terms of volume percentage.

2. The method for removing silicon from biomass capacitor carbon according to claim 1, characterized in that: The total content of calcium and magnesium impurity elements contained in the biomass capacitor carbon particles to be desiliconized is less than 20 ppm.

3. The method for removing silicon from biomass capacitor carbon according to claim 1 or 2, characterized in that: When the moisture content of the biomass capacitor carbon particles to be desiliconized is greater than 200 ppm, the gas phase cleaning agent is 97-99% N2 and 1-3% COF2 by volume.

4. The method for removing silicon from biomass capacitor carbon according to claim 1 or 2, characterized in that: When the moisture content of the biomass capacitor carbon particles to be desiliconized is ≤200 ppm, the gas phase cleaning agent is 95-98% N2, 1-3% COF2 and 1-2% HF by volume.

5. The method for removing silicon from biomass capacitor carbon according to claim 1, characterized in that: The silicon content of the biomass capacitor carbon particles to be desiliconized is ≤500 ppm.

6. The method for removing silicon from biomass capacitor carbon according to claim 1, characterized in that: The biomass capacitor carbon particles to be desiliconized are dried by 50-80° C. dry air to reduce the moisture content.

7. The method for removing silicon from biomass capacitor carbon according to claim 1, 5 or 6, characterized in that: The air flow rate during silicon removal is 0.2-1 L / min, and the reaction time is 1-2h.

8. The method for removing silicon from biomass capacitor carbon according to claim 1, 5 or 6, characterized in that: The biomass capacitor carbon to be desiliconized is piled up to form a fixed bed.

9. The method for removing silicon from biomass capacitor carbon according to claim 1, characterized in that: After desiliconization, the pellets are cooled and the residual gas in the biomass capacitor carbon particles is replaced with nitrogen.

10. The method for removing silicon from biomass capacitor carbon according to claim 9, characterized in that: The residual gas includes one or more of COF2, HF, CO2 and SiF4.

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