Production method of low-carbon hydrogen

Abstract

To solve the problem with complexity of production and increased cost and the problem with energy consumption, in a current method for production of hydrogen with a carbon dioxide laser.SOLUTION: A production method of low-carbon hydrogen according to the present invention includes the steps of: (a) drying waste silicon slurry; (b) crushing and selecting the dried waste silicon slurry to give 40 to 95 percent by weight (wt.%) of silicon oxide in which metal silicon accounts for 5 wt.% to 40 wt.% of a silicon oxide content; and (c) reacting the silicon oxide with an aqueous alkali metal solution by mixture with a reaction temperature controlled between 100°C and 150°C to thereby give hydrogen.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing, in particular, low-carbon hydrogen. [Background technology]

[0002] Semiconductors are deeply involved in the operation of modern electrical devices, with their performance constantly improving, their designs becoming increasingly complex and sophisticated, and their applications expanding. Semiconductors enable us to use laptops, mobile phones, and tablet PCs, promote the development of automotive electronics, avionics, and medical equipment, and significantly improve the energy efficiency of large and small household appliances and lighting fixtures. While semiconductors are an important foundation of modern science and technology, they also produce a large amount of waste. Semiconductor waste contains many heavy metals, including lead and cadmium, which can cause neurological disorders if ingested by the human body, and hexavalent chromium and arsenic, which are carcinogenic. Semiconductor waste also often contains strong acids and alkalis, which, in extreme cases, can pose immediate danger to the human body if they come into contact with the body.

[0003] Waste silicon slurry generated in semiconductor manufacturing processes occurs during the polishing and thinning processes of silicon wafers, when silicon wafers or other substrate materials are planarized using chemical corrosion or machinery. Currently, most of the waste silicon slurry generated during the cutting and polishing processes is separated into solids and liquids through wastewater treatment, concentrated into solids, and collected, and then landfilled by a waste disposal company. However, landfilling waste silicon slurry is prone to environmental pollution, and because waste silicon slurry contains large amounts of silicon dioxide and silicon metal, it is a waste to directly landfill reusable resources.

[0004] Furthermore, with the Earth's petroleum resources becoming limited and environmental awareness increasing, new energy sources that can replace petroleum and are also environmentally friendly are being actively sought for in vehicles, power generation equipment, etc. Among these, fuel cells generate large amounts of electricity by utilizing the reaction between hydrogen and oxygen, making them suitable as a next-generation power source. Although fuel cells are also power generation devices, they are not disposable like ordinary non-rechargeable batteries, and unlike rechargeable batteries, they do not need to be recharged after use. In other words, fuel cells maintain their power by adding fuel, and the fuel they require is hydrogen, which is why they are classified as a new energy source.

[0005] Fuel cells operate by containing two electrodes, a cathode and an anode, separated by a permeable film filled with an electrolyte. Hydrogen enters the fuel cell through the anode, and oxygen (or air) enters through the cathode. Through catalytic action, the hydrogen atoms at the anode are split into two hydrogen protons and two electrons. The protons are attracted to one side of the film by the oxygen, and the electrons are converted into an electric current via an external circuit before reaching the cathode. Through catalytic action at the cathode, the hydrogen protons, oxygen, and electrons react to form water molecules, resulting in the formation of water molecules. Fuel cells are the only waste product of a fuel cell. Because fuel cells generate electricity and water through a chemical reaction between hydrogen and oxygen, they are not only pollution-free but also avoid the long charging times of conventional batteries. They are currently the most promising new energy source. If widely applied to vehicles and other highly polluting power generation devices, they could effectively reduce air pollution and greenhouse gas emissions.

[0006] The current method for producing hydrogen directly for fuel cells involves first using a carbon dioxide laser to decompose silicon into pure silicon powder 10 to 100 nanometers in size, then adding the decomposed pure silicon powder to an alkaline solution to produce hydrogen. However, the equipment and process required to decompose silicon powder using a carbon dioxide laser increases the complexity and cost of hydrogen production and requires additional energy (i.e., the carbon dioxide laser). Furthermore, the size of the silicon powder must be limited to between 10 and 100 nanometers.

[0007] Therefore, in an era where economic circulation and green energy are becoming mainstream, converting waste generated in the semiconductor manufacturing process into reusable hydrogen while also meeting the requirements of energy conservation, low carbon emissions, and a green environment is one of the problems that needs to be solved in this field. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention solves the problems of the current method of using a carbon dioxide laser to decompose silicon into pure silicon powder with a size of 10 to 100 nanometers, and then adding the decomposed pure silicon powder to an alkaline solution to produce hydrogen, which increases the complexity and cost of production and also reduces the energy consumption. [Means for solving the problem]

[0009] In view of the above, the present invention provides a method for producing low-carbon hydrogen, which has the effects of energy saving and low carbon, and also meets the requirements of a green environment.

[0010] To achieve the above objectives, the method for producing low-carbon hydrogen of the present invention includes steps (a), (b), and (c): step (a) is drying waste silicon slurry; step (b) is crushing and sorting the dried waste silicon slurry to obtain silicon oxide (SiOx, x=0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (SiOx, x=0) accounts for 5 wt% to 40 wt% of the silicon oxide content; step (c) is mixing and reacting the silicon oxide from step (b) with an alkali metal aqueous solution, controlling the reaction temperature between 100°C and 150°C, thereby producing hydrogen.

[0011] In one embodiment, the waste silicon slurry of step (a) is generated in a semiconductor manufacturing process.

[0012] In one embodiment, the moisture content of the dried waste silicon slurry in step (a) is less than 10 wt %.

[0013] In one embodiment, the aqueous alkali metal solution in step (c) is aqueous sodium hydroxide.

[0014] In one embodiment, the concentration of the sodium hydroxide solution is 45 wt%.

[0015] In one embodiment, in step (c), the reaction temperature of the silicon oxide and the aqueous alkali metal solution is controlled to be between 100°C and 150°C by controlling the content of metallic silicon in the silicon oxide.

[0016] In one embodiment, the higher the silicon metal content, the closer the reaction temperature is to 150°C.

[0017] In one embodiment, in step (c), the reaction time is 2 hours or more.

[0018] As described above, in the method for producing low-carbon hydrogen of the present invention, hydrogen is produced by using waste silicon slurry to reach the required reaction temperature through a self-exothermic reaction between metallic silicon contained in silicon oxide and an alkali metal aqueous solution. As a result, compared to current methods for producing hydrogen using carbon dioxide lasers, the method for producing hydrogen of the present invention can produce hydrogen without consuming additional energy, thereby achieving energy-saving and low-carbon effects. Furthermore, because the raw material waste silicon slurry used is a process waste generated in the semiconductor manufacturing process, the method for producing hydrogen of the present invention meets the requirements for a green environment. [Effects of the Invention]

[0019] The method for producing low-carbon hydrogen provided by the present invention not only has the effects of energy saving and low carbon emissions, but also meets the requirements of a green environment. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a flow diagram of a method for producing low-carbon hydrogen according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The method for producing low-carbon hydrogen of the present invention will be described with reference to the drawings. Note that the same elements will be denoted by the same reference numerals.

[0022] Figure 1 is a flow diagram of a method for producing low-carbon hydrogen according to one embodiment of the present invention. As shown in Figure 1, the method for producing low-carbon hydrogen according to the present invention includes steps (a) to (c). Each step will be described in detail below.

[0023] First, in step (a), waste silicon slurry is dried. Waste silicon slurry is generated during the semiconductor manufacturing process, and examples thereof include, but are not limited to, waste silicon wafers, waste silicon slurry generated during the silicon wafer cutting process, silicon wafer polishing, and packaging and package inspection processes. In step (a), the waste silicon slurry generated during the semiconductor manufacturing process is placed in a drying furnace and dried to remove moisture, resulting in a dried waste silicon slurry with a moisture content of less than 10 wt% (weight percentage).

[0024] Next, in step (b), the dried waste silicon slurry is crushed and separated to obtain silicon oxide (SiOx, x = 0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (Si / SiOx, x = 0) accounts for 5 to 40 wt% of the silicon oxide content. Here, the waste silicon slurry is classified based on the metallic silicon content, and silicon oxide with a content of 40 to 95 wt% is separated from the waste silicon slurry, and metallic silicon (Si) accounts for 5 to 40 wt% of the silicon oxide content. The purpose of this is to control the reaction temperature in the subsequent mixing reaction in step (c), i.e., by controlling the metallic silicon content, the temperature required for the chemical reaction in step (c) can be reached.

[0025] Then, in step (c), the silicon oxide from step (b) is mixed and reacted with an aqueous alkali metal solution, and hydrogen is obtained by controlling the reaction temperature between 100°C and 150°C. In step (c), as described above, the reaction temperature during reaction with the aqueous alkali metal solution is controlled by controlling the metallic silicon (Si) content in the silicon oxide, and by setting the reaction temperature between 100°C and 150°C, an aqueous sodium silicate solution is obtained. Furthermore, the higher the metallic silicon content in the silicon oxide, the higher the reaction temperature, approaching 150°C. Furthermore, in step (c), the reaction time during which the silicon oxide and the aqueous alkali metal solution are mixed and reacted is set to 2 hours or more, thereby allowing the silicon oxide and the aqueous alkali metal solution to react sufficiently.

[0026] In some embodiments, the alkali metal aqueous solution may be, but is not limited to, aqueous sodium hydroxide (NaOH(aq)). The concentration of the aqueous sodium hydroxide is, for example, 45 wt%. In some embodiments, the silicon oxide obtained in step (b) and an aqueous sodium hydroxide solution with a concentration of 45 wt% are added to a reactor, and the metallic silicon content in the silicon oxide is controlled to be between 5 wt% and 40 wt%. By utilizing the self-exothermic reaction that occurs when silicon oxide (metallic silicon) reacts with sodium hydroxide, the reaction temperature is controlled to be between 100°C and 150°C, and hydrogen (H2) is obtained after 2 hours of reaction.

[0027] The reaction scheme for step (c) is as follows: Si + 2H2O → SiO2 + 2H2 + heat (339 KJ / mole) ··· Reaction Equation (1) SiO2 + 2NaOH → Na2SiO3 + H2O + heat (85 KJ / mole) ··· Reaction equation (2).

[0028] In some applications, hydrogen can be used in fuel cells, which generate electricity and water through a chemical reaction between hydrogen and oxygen. This is not only pollution-free (the product is water), but also avoids the problem of long charging times for conventional batteries. If hydrogen can be widely used in vehicles and other highly polluting power generation devices, it can effectively reduce air pollution and greenhouse gas emissions.

[0029] It is worth noting that in some applications described later, step (c) involves reacting sodium silicate aqueous solution with sulfuric acid (H2SO4), followed by solid-liquid separation and drying to obtain silicon dioxide (SiO2). The reaction time is between 30 minutes and 2 hours, and the purity of the resulting silicon dioxide is, for example, greater than 94 wt%. The reaction formula is as follows: Na2SiO3+H2SO4→Na2SO4+SiO2+H2O

[0030] The sulfuric acid concentration is between 30wt% and 80wt%, and it can also be waste sulfuric acid generated in the semiconductor manufacturing process. For example, in silicon wafer factories, high-purity sulfuric acid is used to clean the surface of silicon wafers, mainly after removing the photoresist. The sulfuric acid used is added with hydrogen peroxide (H2O2), which acts as a strong oxidizing agent, decomposing the organic matter on the chips into CO2 and H2O, generating waste sulfuric acid. The application of this waste sulfuric acid can also achieve the goals of economic circulation and resource reuse.

[0031] The following six examples demonstrate that hydrogen can be reliably produced by the production method of the present invention (see Table 1).

[0032] Example 1

[0033] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 50.52wt%, metallic silicon accounts for 9.36wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali (sodium hydroxide aqueous solution) and 20g of water, then stir evenly in a reactor to react, the reaction temperature can be naturally heated to 103.8℃ due to exothermic reaction, and after 2 hours of reaction 0.492L of hydrogen can be obtained.

[0034] Example 2

[0035] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 58.07wt%, metallic silicon accounts for 12.74wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali and 20g of water, and then stir and react evenly in a reactor. The reaction temperature can be naturally heated to 119.6℃ through exothermic reaction, and after 2 hours of reaction, 0.670L of hydrogen can be obtained.

[0036] Example 3

[0037] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 76.39wt%, metallic silicon accounts for 14.49wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali and 20g of water, and then stir and react evenly in a reactor, allowing the reaction temperature to naturally heat up to 135°C through exothermic reaction, and after 2 hours of reaction, 0.762L of hydrogen is obtained.

[0038] Example 4

[0039] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 75.80wt%, metallic silicon accounts for 16.61wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali and 20g of water, and then stir evenly in a reactor to react. The reaction temperature can be naturally heated to 142°C through exothermic reaction, and after 2 hours of reaction, 0.874L of hydrogen can be obtained.

[0040] Example 5

[0041] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 76.92wt%, metallic silicon accounts for 20.16wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali and 20g of water, and then stir and react evenly in a reactor. The reaction temperature can be naturally heated to 145°C through exothermic reaction, and after 2 hours of reaction, 1.060L of hydrogen can be obtained.

[0042] Example 6

[0043] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 82.16wt%, metallic silicon accounts for 32.60wt% of silicon oxide), add 3.9g of 45% concentration liquid alkali and 20g of water, and then stir evenly in a reactor to react. The reaction temperature can be naturally heated to 149.5℃ through exothermic reaction, and after 2 hours of reaction, 1.724L of hydrogen can be obtained.

[0044] The six examples described above are summarized in Table 1.

[0045] [Table 1]

[0046] As can be seen from the six examples above, the present invention does not produce hydrogen using conventional equipment and processes that decompose silicon powder using a carbon dioxide laser, but rather uses waste silicon slurry to produce hydrogen by reaching the required reaction temperature through a self-exothermic reaction between the metallic silicon content in silicon oxide and an alkali metal (sodium hydroxide) aqueous solution, thereby producing hydrogen without consuming additional energy, resulting in energy-saving and low-carbon effects.In addition, because the waste silicon slurry used as the raw material is a waste product generated in the semiconductor manufacturing process, the manufacturing method of the present invention meets the requirements of a green environment.

[0047] In summary, in the method for producing low-carbon hydrogen of the present invention, hydrogen is produced by using waste silicon slurry to reach the required reaction temperature through a self-exothermic reaction between metallic silicon contained in silicon oxide and an alkali metal aqueous solution. As a result, compared to the current method of producing hydrogen using a carbon dioxide laser, the method of the present invention can produce hydrogen without consuming additional energy, thereby achieving energy-saving and low-carbon effects. Furthermore, because the waste silicon slurry used as a raw material is a process waste generated in the semiconductor manufacturing process, the method of the present invention meets the requirements for a green environment.

[0048] The above are only some of the embodiments of the present invention, and are not intended to limit the present invention. Any modifications or changes made without departing from the spirit and scope of the present invention should fall within the scope of the claims of the present invention. [Industrial Applicability]

[0049] The manufacturing method of the present invention uses waste silicon slurry to produce hydrogen by the self-exothermic reaction between the metallic silicon contained in silicon oxide and an alkali metal aqueous solution, which reaches the required reaction temperature.Compared to the current method of producing hydrogen using a carbon dioxide laser, the present invention meets the requirements of energy saving, low carbon emissions and green environment. [Explanation of symbols]

[0050] a, b, c process

Claims

1. (a) a step of drying the waste silicon slurry; (b) crushing and sorting the dried waste silicon slurry to obtain silicon oxide (SiOx, x=0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (SiOx, x=0) accounts for 5 wt% to 40 wt% of the silicon oxide content; and step (c) of mixing and reacting the silicon oxide of step (b) with an aqueous alkali metal solution and controlling the reaction temperature to a range of 100°C to 150°C to obtain hydrogen.

2. 2. The method for producing low-carbon hydrogen according to claim 1, wherein the waste silicon slurry in step (a) is generated in a semiconductor manufacturing process, and the moisture content of the dried waste silicon slurry is less than 10 wt %.

3. 2. The method for producing low-carbon hydrogen according to claim 1, wherein the aqueous alkali metal solution in step (c) is an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is 45 wt %.

4. 2. The method for producing low-carbon hydrogen according to claim 1, wherein in step (c), the reaction temperature of the silicon oxide and the alkali metal aqueous solution is controlled to be between 100°C and 150°C by controlling the metallic silicon content in the silicon oxide.

5. The method for producing low-carbon hydrogen according to claim 4, wherein the reaction temperature approaches 150°C as the content of the metallic silicon increases.

6. 2. The method for producing low-carbon hydrogen according to claim 1, wherein the reaction time in step (c) is 2 hours or more.

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