JP2015093808A - Silicon raw material a for producing hydrogen gas, silicon raw material b for producing hydrogen gas, method of producing silicon raw material a for producing hydrogen gas, method of producing silicon raw material b for producing hydrogen gas, method and apparatus for producing hydrogen gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously obtain hydrogen gas by appropriately suppressing a reaction between silicon particles and an alkali aqueous solution, in hydrogen gas production using the reaction between silicon particles and an alkali aqueous solution.SOLUTION: A silicon raw material A for producing hydrogen gas contains silicon particles and an oil content. The oil content is 0.1 wt.% to 10 wt.% of the silicon particles. A method of producing the silicon raw material A for producing hydrogen gas includes a step of preparing silicon scrap 108 containing silicon particles, the oil content and water, a step of producing solid matter A 112 containing the silicon particles, the oil content and a small amount of water by centrifugal separation or filtration of the silicon scrap 108, a step of producing a solid matter B 115 containing the silicon particles and the oil content by drying the solid matter A 112 and a step of obtaining a sludge A 117 by mixing the solid matter B 115 with water 116.

Description

  The present invention relates to a silicon raw material A for hydrogen gas production, a silicon raw material B for hydrogen gas production, a method for producing silicon raw material A for hydrogen gas production, a method for producing silicon raw material B for hydrogen gas production, a hydrogen gas production method, and hydrogen gas production. Relates to the device.

  Currently, a large amount of silicon wafers are used as substrates for semiconductor devices. A silicon wafer is manufactured as follows. First, a cylindrical silicon ingot is manufactured by crystal growth from molten silicon. Next, an orientation flat or notch indicating the direction of the crystal axis is formed in the silicon ingot. Next, the silicon ingot is sliced to a predetermined thickness to produce a silicon wafer. Slicing is done with a dicer or multi-wire saw. Next, lapping processing for cutting to a predetermined thickness, etching processing for removing processing distortion, beveling processing for preventing peripheral chipping, mirror polishing processing for making the surface a mirror surface, and the like are performed on the silicon wafer. In the manufacturing process of such a silicon wafer, a large amount of silicon waste is generated. Conventionally, silicon scraps are discarded, but the cost burden and environmental burden due to disposal cannot be ignored.

On the other hand, it is known that hydrogen gas is generated when silicon is heated in an alkaline aqueous solution (for example, NaOH aqueous solution). Generation of hydrogen gas is Si + 2OH ⁻ + H ₂ O → SiO ₃ ²⁻ + 2H ₂ ↑
It depends on the reaction. Therefore, if hydrogen gas can be efficiently obtained from silicon waste, it is very advantageous in terms of cost load and environmental load.

  Attempts to obtain hydrogen gas from silicon waste have been made for some time. For example, in patent document 1 (Unexamined-Japanese-Patent No. 2000-191303), silicon waste and aqueous alkali solution are put into the reaction tank which can be sealed, a reaction tank is heated, silicon waste and alkaline aqueous solution are made to react, and the generated hydrogen gas is collected. However, as a feature of the reaction between silicon and an aqueous alkali solution, the reaction proceeds abruptly immediately after the start of the reaction, but the reaction stops thereafter. Therefore, it is difficult to control the generation of hydrogen gas.

Further, as can be seen from the reaction formula, silicate ions (SiO ₃ ²⁻ ) are generated in the reaction between silicon and the aqueous alkali solution. If the aqueous alkali solution or silicon is excessive, the silicate ions form a gel and cover the unreacted silicon, thereby inhibiting the reaction, that is, the generation of hydrogen gas.

  In order to solve these problems, in Patent Document 2 (Japanese Patent Laid-Open No. 2001-213609), silicon powder is mixed with water and supplied as sludge (mud). By supplying the silicon powder with sludge, the intense reaction immediately after the contact between the silicon and the aqueous alkali solution is suppressed, and the generation of gel-like silicate ions is also suppressed. In addition, hydrogen gas can be continuously obtained by taking out hydrogen gas from the reaction vessel and adding silicon sludge or an aqueous alkali solution so that the pressure in the reaction vessel is maintained within a predetermined range. .

JP 2000-191303 A Japanese Patent Laid-Open No. 2001-213609

  The inventor of the present application conducted an experiment of mixing silicon powder with water and supplying it with sludge, as in Patent Document 2. Although the content will be described later as an explanation of the comparative example of FIG. 3 of the present application, as a result, even if silicon powder is mixed with water and supplied as sludge, the intense reaction immediately after the contact between silicon and the aqueous alkali solution cannot be suppressed. It was.

  Further, in the hydrogen gas production apparatus of Patent Document 2, silicon powder is mixed with water, but in an actual multi-wire saw, the silicon ingot and the wire are cut while being cooled with a coolant. The coolant is not mere water, but a liquid obtained by mixing water with, for example, propylene glycol (PG). Propylene glycol reduces the surface tension of water and improves the wettability of the wire and the penetration of the silicon ingot into the slicing grooves. Propylene glycol or a material having a similar function is called oil in the coolant.

  For this reason, silicon particles and coolant (water and oil) are contained in the silicon scrap generated from the multi-wire saw. In this respect, since “sludge in which silicon powder is mixed with water” in Patent Document 2 does not contain oil, it differs from silicon scrap actually generated from a multi-wire saw. Since the silicon scrap generated from the multi-wire saw contains a coolant, the oil in the coolant covers the surface of the silicon particles, preventing the contact between the silicon particles and the alkaline aqueous solution, thereby inhibiting the reaction. Therefore, the amount of hydrogen gas generation is less than the theoretical value. The first object of the present invention is to prevent the oil in the coolant from inhibiting the generation of hydrogen gas.

However, according to the experiments of the present inventor, when the oil is completely removed, the reaction proceeds explosively immediately after the start of the reaction, and does not react at all thereafter. The reason is as follows. In the reaction between the silicon particles and the aqueous alkali solution, the following three reactions occur sequentially on the surface of the silicon particles.
Si + 2OH ⁻ → Si (OH) ₂ ²⁺ + 4e ⁻ (1)
4H ₂ O + 4e ⁻ → 4OH ⁻ + 2H ₂ ↑ (2)
Si (OH) ₂ ²⁺ + 4OH ⁻ → SiO ₂ (OH) ₂ ² + + 2H ₂ O (3)
These three formulas are collectively expressed by the following formula.
Si + 2OH ⁻ + 2H ₂ O → 2SiO ₂ (OH) ₂ ²⁻ + 2H ₂ ↑ + 423.8 kJ (4)
Thus, 1 mole of silicon particles reacts with 2 moles of alkali and 2 moles of water, 2 moles of SiO ₂ (OH) ₂ ²⁻ (hydrate of metasilicate ion and water-soluble) and 2 Molar hydrogen gas is generated.

  The alkaline aqueous solution in the reaction tank consumes twice the number of moles of silicon particles, and then comes out of the reaction tank as alkali mist together with the generated hydrogen gas and water vapor. The alkaline aqueous solution deficient in the reaction tank is immediately replenished with a pump from the alkaline aqueous solution tank. Not only is water consumed in the above reaction, but the water corresponding to the saturated water vapor pressure at the reaction vessel temperature evaporates with hydrogen gas, so the shortage is replenished from the water in the sludge tank and the water in the alkaline aqueous solution tank. Is done.

When an aqueous NaOH solution is used as the aqueous alkaline solution,
Si + 2NaOH + H ₂ O → Na ₂ SiO ₃ + 2H ₂ ↑ + 423.8 kJ
An exothermic reaction occurs. The calorific value of this reaction is very large, about 10 times the heat of vaporization of water and about twice the heat of combustion of hydrogen. That is, when silicon particles are mixed with an aqueous NaOH solution, hydrogen gas twice as much as the mixed silicon particles is generated and reaction heat twice as much as that when the hydrogen gas burns is generated. When the temperature of the reaction system rises due to the heat of reaction, the reaction rate increases and the heat of reaction increases. Because of this positive feedback, the reaction between the silicon particles and the aqueous alkali solution becomes explosive and very difficult to control. Such a reaction state is called thermal runaway.

  If silicon is a fine particle of several μm, the surface area is large, so that the thermal runaway of the reaction becomes more severe and the control becomes more difficult. The temperature rise of the mixture of silicon particles and aqueous alkali solution generated by reaction heat cannot be suppressed even if the reaction vessel is cooled. Therefore, conventionally, it has been difficult to control the generation of hydrogen gas by the reaction between silicon particles and an aqueous alkali solution. The second object of the present invention is to moderately suppress the reaction between silicon particles and an aqueous alkali solution so that hydrogen gas can be obtained constantly.

  In the hydrogen gas production apparatus of Patent Document 2, silicon sludge and an aqueous alkali solution are additionally supplied so that the pressure in the reaction tank is maintained within a predetermined range while taking out the hydrogen gas from the reaction tank. Thereby, it is supposed that hydrogen gas can be obtained continuously. However, according to FIG. 6 of Patent Document 2, the pressure in the reaction vessel fluctuates in the range of 0.1 MPa to 0.2 MPa, and cannot be said to be stable. Moreover, since FIG. 6 shows a simulation result that does not consider reaction heat, the situation seems to be different from an actual reaction in which a large amount of reaction heat is generated. Further, the sludge is intermittently supplied every about 13 minutes, and it is not a system for continuously and stably controlling the generation of hydrogen gas.

  Then, the 3rd subject of this invention is implement | achieving the hydrogen gas manufacturing method and hydrogen gas manufacturing apparatus with little pressure fluctuation of a reaction tank. The third problem (method and apparatus for producing hydrogen gas with little pressure fluctuation) is closely related to the second problem (moderately suppresses the reaction between silicon particles and an aqueous alkali solution). The third problem (hydrogen gas production device with little pressure fluctuation) cannot be solved unless the reaction between the aqueous solution and the alkaline aqueous solution is moderately suppressed.

  In the Example of patent document 1, the capacity | capacitance of a reaction tank is 0.2 liter. Although the capacity of the reaction tank is not described in the example of Patent Document 2, since the alkaline aqueous solution (NaOH aqueous solution) is 1 liter, the capacity of the reaction tank is estimated to be several liters. According to the research of the present inventor, this problem is not a problem with a laboratory hydrogen gas production apparatus of this scale, but the following problems occur with a mass production hydrogen production apparatus with a scale of 10 to 100 times.

Si + 2OH ⁻ + H ₂ O → SiO ₃ ²⁻ + 2H _{2 of} silicon particles and aqueous alkali solution ↑
From this reaction equation, what is generated from the reaction vessel seems to be only hydrogen gas and water vapor. Therefore, in Patent Documents 1 and 2, a condenser is coupled to the reaction tank. The condenser is a device that cools the gas mixture of hydrogen gas and water vapor to lower the dew point of the gas mixture, condenses the water vapor into water, and removes water vapor from the gas mixture.

  However, according to the research of the present inventor, in a mass production scale hydrogen gas production apparatus, in addition to hydrogen gas and water vapor, in addition to hydrogen gas and water vapor, alkaline aqueous solution mist (misty alkaline aqueous solution), metasilicate hydrate mist, and silicon particles are also produced. Scatter. For this reason, in the case of a mass production scale hydrogen gas production apparatus, when a condenser is connected to the reaction tank, alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles enter the condenser.

  Alkaline aqueous solution mist solidifies when it is cooled to a low temperature by a condenser. The alkaline aqueous solution mist corrodes the condenser depending on the material of the condenser. Silicon particles are deposited in the condenser. As the deposition of silicon particles proceeds, the tube inside the condenser becomes clogged. Accordingly, a fourth problem of the present invention is to prevent corrosion and clogging due to alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles.

[Silicon raw material A for hydrogen gas production]
When the coolant contains oil, the silicon raw material A for producing hydrogen gas according to the present invention does not completely remove the oil in the coolant, but leaves an appropriate amount when the silicon particles are refined. Since the oil component inhibits the reaction between the silicon particles and the aqueous alkali solution, hydrogen gas is not generated if the oil component is excessive. Conversely, if the oil content is too small, hydrogen gas is explosively generated and cannot be controlled. Therefore, an appropriate amount of coolant remains. Since silicon particles and oil alone are solid, continuous supply by a pump is difficult. Therefore, add water to make sludge.
(1) The silicon raw material A for hydrogen gas production of the present invention contains silicon particles, 0.1 wt% to 10 wt% oil content of the silicon particles, and water.
(2) In the silicon raw material A for hydrogen gas production of the present invention, the oil content is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
Or a mixture thereof. These substances may be contained as oils in the coolant.
(3) In the silicon raw material A for hydrogen gas production of the present invention, the average particle size of the silicon particles is 0.1 μm to 30 μm. When the average particle size of the silicon particles is less than 0.1 μm, the oil reaction suppression effect may be insufficient. If the average particle diameter of the silicon particles exceeds 30 μm, the surface area of the silicon particles may be insufficient and the reaction may be insufficient. In addition, silicon particles are likely to precipitate and may not be uniformly dispersed in the aqueous alkali solution.
(4) In the silicon raw material A for hydrogen gas production of the present invention, the weight of water is 1 to 10 times the weight of silicon particles. If the weight of water is less than one time the weight of silicon particles, the viscosity of the sludge may be too high, making it difficult to supply with a sludge pump. If the weight of water exceeds 10 times the weight of silicon particles, the balance between the silicon particles and the aqueous alkali solution will be lost (the concentration of the aqueous alkali solution will be too thin), or the liquid temperature of the liquid mixture in the reaction tank will decrease. As a result, the generation rate of hydrogen gas may decrease.

[Silicon raw material B for hydrogen gas production]
The silicon raw material B for producing hydrogen gas of the present invention is obtained by removing most of the oil in the coolant that inhibits the hydrogen gas generation reaction when refining silicon particles, and newly adding a reaction inhibitor. The reaction-suppressing substance is a substance having a function of suppressing the reaction between the silicon particles and the alkaline aqueous solution, like the oil. However, the reaction-suppressing substance used for the silicon raw material B for producing hydrogen gas of the present invention usually includes a substance not included in the coolant. The reaction-suppressing substance is added after removing oil in the coolant that inhibits the hydrogen gas generation reaction. If the oil content in the coolant remains, both the oil content and the reaction-suppressing substance produce a reaction-suppressing action, so that delicate control of the reaction-suppressing action is difficult. Therefore, after removing the oil in the coolant, a reaction inhibitor is added.
(5) The silicon raw material B for hydrogen gas production of the present invention contains silicon particles, 0.1 wt% to 10 wt% of a reaction suppressing substance of the silicon particles, and water.
(6) In the silicon raw material B for hydrogen gas production of the present invention, the reaction inhibitor is
Formic acid, lactic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, acrylic acid, oleic acid , Malic acid, citric acid, oxalic acid, maleic acid, fumaric acid,
Vinyl pyrrolidone, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene oxide, polyethylene imide, polyvinyl alcohol, polyacrylamide, polyethylene glycol,
Or a mixture thereof.
(7) In the silicon raw material B for hydrogen gas production of the present invention, the average particle size of the silicon particles is 0.1 μm to 30 μm.
(8) In the silicon raw material B for hydrogen gas production of the present invention, the weight of water is 1 to 10 times the weight of silicon particles.

[Method for producing silicon raw material A for hydrogen gas production]
The method for producing the silicon raw material A for producing hydrogen gas according to the present invention is characterized in that an appropriate amount of coolant oil (0.1 wt% to 10 wt% of the silicon particles) is left when the silicon particles are purified.
(9) The method for producing the silicon raw material A for producing hydrogen gas according to the present invention comprises:
Preparing silicon scraps containing oil and water derived from silicon particles and coolant,
A step of producing a solid A containing silicon particles, 0.1 wt% to 10 wt% oil of the silicon particles, and a small amount of water by centrifuging or filtering the silicon waste;
Drying the solid A to produce a solid B containing silicon particles and an oil content of 0.1 wt% to 10 wt% of the silicon particles;
A step of producing sludge A by adding water to the solid B;
(10) In the method for producing the silicon raw material A for producing hydrogen gas of the present invention, the oil content is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
Or a mixture thereof.
(11) In the method for producing silicon raw material A for producing hydrogen gas of the present invention, the drying temperature of the solid A is 100 ° C to 120 ° C. This drying temperature is a temperature at which water evaporates but oil does not evaporate.

[Method for producing silicon raw material B for hydrogen gas production]
In the method for producing silicon raw material B for hydrogen gas production of the present invention, when refining silicon particles, oil that inhibits the hydrogen gas generation reaction in the coolant is almost removed in the high-temperature drying step, and then a new reaction is performed. It is characterized by adding inhibitory substances.
(12) The method for producing the silicon raw material B for producing hydrogen gas of the present invention comprises:
Preparing silicon scraps containing oil and water derived from silicon particles and coolant,
Centrifuge or filter silicon waste to produce a solid A containing silicon particles, oil and a small amount of water,
Drying the solid A to produce a solid B containing silicon particles and oil;
A step of producing a solid C composed of silicon particles by drying the solid B at a high temperature to evaporate the oil;
A step of producing sludge B by adding 0.1 wt% to 10 wt% of a reaction inhibiting substance of silicon particles and water to solid C is included.
(13) In the method for producing the silicon raw material B for hydrogen gas production of the present invention, the reaction inhibitor is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
Formic acid, lactic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, acrylic acid, oleic acid , Malic acid, citric acid, oxalic acid, maleic acid, fumaric acid,
Vinyl pyrrolidone, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene oxide, polyethylene imide, polyvinyl alcohol, polyacrylamide, polyethylene glycol,
Or a mixture thereof.
(14) In the method for producing the silicon raw material B for hydrogen gas production of the present invention, the drying temperature of the solid A is 100 ° C to 120 ° C. This drying temperature is a temperature at which water evaporates but oil does not evaporate.
(15) In the method for producing the silicon raw material B for hydrogen gas production of the present invention, the high temperature drying temperature of the solid B is 500 ° C to 700 ° C. This high temperature drying temperature is a temperature at which the oil contained in the solid B is almost evaporated.

[Method for producing hydrogen gas]
The hydrogen gas production method of the present invention uses the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production of the present invention, and the injection rate of the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production is increased. Feedback control based on the temperature of the liquid mixture in the reaction tank, feedback control of the injection rate of the alkaline aqueous solution based on the alkali concentration in the reaction tank, hydrogen gas, water vapor, alkaline aqueous solution mist, metasilicate hydrate The gas P containing mist and silicon particles is treated with a scrubber to remove alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles from the gas P.
(16) The hydrogen gas production method of the present invention comprises:
Preparing a silicon raw material A for hydrogen gas production or a silicon raw material B for hydrogen gas production;
Preparing an alkaline aqueous solution,
A step of injecting the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production into the reaction tank while feedback control of the injection speed based on the temperature of the mixed liquid in the reaction tank;
A step of injecting an aqueous alkali solution into the reaction vessel while controlling the injection rate based on the alkali concentration in the reaction vessel,
Maintaining the mixed liquid of the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production and the alkaline aqueous solution in the reaction tank at a predetermined temperature;
The gas P containing hydrogen gas, water vapor, alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles taken out from the reaction tank is treated with a scrubber, and the alkaline aqueous solution mist, metasilicate hydrate mist from the gas P, Removing silicon particles;
It includes a step of removing the water vapor from the gas Q by treating the gas Q containing hydrogen gas and water vapor, which is treated with a scrubber, with a condenser.
(17) In the hydrogen gas production method of the present invention, the alkaline aqueous solution is a NaOH aqueous solution or a KOH aqueous solution.
(18) In the hydrogen gas production method of the present invention, the concentration of the NaOH aqueous solution or the KOH aqueous solution is 1 mol / L to 8 mol / L.
(19) In the hydrogen gas production method of the present invention, the predetermined temperature is 50 ° C to 90 ° C.

[Hydrogen gas production equipment]
(20) The hydrogen gas production apparatus of the present invention comprises:
A sealable reaction vessel;
Means for supplying the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production to the reaction vessel;
Means for supplying an aqueous alkaline solution to the reaction vessel;
A thermometer, heater and cooler provided in the reaction vessel;
A scrubber, a condenser, and a regulator are provided in this order on the hydrogen gas extraction side of the reaction tank.
(21) In the hydrogen gas production apparatus of the present invention, the scrubber removes the alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles generated from the reaction vessel.
(22) In the hydrogen gas production apparatus of the present invention, the means for supplying the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production is preferably a Mono pump or a gear pump. Mono pumps and gear pumps can stably discharge sludge material.
(23) In the hydrogen gas production apparatus of the present invention, the reaction tank includes means for mixing the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production with an alkaline aqueous solution.

  The silicon raw material A for producing hydrogen gas of the present invention contains an appropriate amount of oil that moderately suppresses the reaction between the silicon particles and the alkaline aqueous solution. The oil comes from the coolant. The silicon scrap obtained by separating the regenerated coolant from the waste coolant of the multi-wire saw contains more than 10% of the weight of silicon particles. Thus, when there is too much oil content contained in silicon | silicone waste, reaction of a silicon particle and aqueous alkali solution is inhibited. Therefore, even when an alkaline aqueous solution is added to silicon scrap, the hydrogen gas obtained is less than the theoretical value. Such silicon scrap cannot be used as it is as a silicon raw material for producing hydrogen gas.

  Since the silicon raw material for producing hydrogen gas of the present invention contains less oil than silicon scrap, hydrogen gas as the theoretical value can be obtained by adding an alkaline aqueous solution. Moreover, the silicon raw material for producing hydrogen gas of the present invention contains an appropriate amount of oil (0.1 wt% to 10 wt% of the silicon particles) that suppresses the reaction between the silicon particles and the aqueous alkali solution. Does not become explosive. Thereby, reaction of silicon particles and aqueous alkali solution is moderately suppressed, and hydrogen gas can be generated constantly over a long period of time. As a result, the first problem (oil inhibits the generation of hydrogen gas) and the second problem (moderately suppresses the reaction between the silicon particles and the aqueous alkali solution) are solved simultaneously.

  The silicon raw material B for hydrogen gas production of the present invention is obtained by evaporating and removing the oil component derived from the coolant by high-temperature drying, and then mixing a desired amount of a reaction suppressing substance with silicon particles in a desired amount. The reaction-suppressing substance is a substance having a function of appropriately suppressing the reaction between the silicon particles and the alkaline aqueous solution, like the oil. The mechanism by which the reaction inhibitor moderately suppresses the reaction between the silicon particles and the aqueous alkali solution is the same as the mechanism by the oil component derived from the coolant. As the reaction suppressing substance contained in the silicon raw material B for hydrogen gas production, a substance different from the oil content of the coolant is usually used, but the same material as the oil content of the coolant may be used. Even when the silicon raw material B for producing hydrogen gas is used, the reaction between the silicon particles and the aqueous alkali solution is moderately suppressed, and hydrogen gas can be generated constantly over a long period of time.

  The silicon raw material for producing hydrogen gas of the present invention is made into sludge by adding water having a weight of 1 to 10 times, preferably 1 to 5 times, more preferably 2 to 4 times the weight of silicon particles. is there. Thereby, it can inject | pour accurately into a reaction tank with a sludge pump.

  Since the method for producing the silicon raw material A for producing hydrogen gas of the present invention uses the oil contained in the coolant, the production process is short. On the other hand, in the method for producing the silicon raw material B for hydrogen gas production of the present invention, any reaction suppressing substance can be mixed with high accuracy.

  In the hydrogen gas production method of the present invention, since the injection rate of the silicon raw material for hydrogen gas production and the aqueous alkali solution is continuously injected while feedback control is performed based on the temperature and alkali concentration of the mixture in the reaction tank, a certain amount of hydrogen Gas is obtained continuously. The reason why the alkaline aqueous solution and the silicon raw material can be continuously injected is that the second problem (moderately suppressing the reaction between the silicon particles and the alkaline aqueous solution) has been solved. Thereby, the 3rd subject (pressure fluctuation of a reaction tank) is solved.

  In the hydrogen gas production apparatus of the present invention, a scrubber is provided between the reaction tank and the condenser. Hydrogen gas generated in the reaction vessel is led to a scrubber. The scrubber removes the aqueous alkali mist, metasilicate hydrate, and silicon particles scattered from the reaction vessel before entering the condenser. This solves the fourth problem (corrosion and clogging with alkaline aqueous solution mist, metasilicate hydrate, silicon particles).

Production flow chart of silicon raw material for producing hydrogen gas of the present invention Configuration diagram of the hydrogen gas production apparatus of the present invention Graph of hydrogen gas production experiment (effect of reaction inhibitor) Graph of hydrogen gas production experiment (Example 1) Graph of hydrogen gas production experiment (Example 2)

  In order to solve the first problem (the oil in the coolant inhibits the generation of hydrogen gas) and the second problem (moderately suppresses the reaction between the silicon particles and the aqueous alkali solution), the silicon raw material for producing hydrogen gas of the present invention A and silicon raw material B for hydrogen gas production are produced according to the flowchart of FIG.

  As shown in the flowchart of FIG. 1, a silicon ingot 102 is set on a multi-wire saw 101, and the silicon ingot 102 is cut while being cooled with a coolant 103 (mixed liquid of water and oil) to manufacture a silicon wafer 104. The portion cut by the wire (cutting margin, kerf loss) becomes amorphous silicon particles having a size of about 0.1 μm to 30 μm. In the silicon raw material A for producing hydrogen gas and the silicon raw material B for producing hydrogen gas of the present invention, the average particle size of the silicon particles is preferably about 1 μm. Waste coolant 105 generated in the multi-wire saw 101 includes silicon particles and coolant 103. The oil component contained in the coolant 103 is, for example, propylene glycol.

  As shown in the flowchart of FIG. 1, the waste coolant 105 is first subjected to a centrifuge A106 to be separated into a supernatant and a precipitate. The supernatant contains water and oil and is used again in the multi-wire saw 101 as the regenerated coolant 107. The precipitate is called silicon scrap 108, and contains water, oil, and silicon particles. Since the silicon scrap 108 contains an oil component that exceeds 10% of the weight of the silicon particles, the reaction with the alkaline aqueous solution tends to be hindered.

  As shown in the flowchart of FIG. 1, in order to reduce the oil content in the silicon waste 108, the silicon waste 108 is again applied to the centrifuge B 109 or passed through the filter 110. When the silicon waste 108 is centrifuged again, the supernatant 111 contains water and oil. This supernatant 111 is discarded. The centrifugal precipitate is a solid A112 mainly composed of silicon particles, and contains oil (0.1 wt% to 10 wt% of the silicon particles) and a small amount of water.

  When the silicon waste 108 is passed through the filter 110, the filtrate 113 contains water and oil. This filtrate 113 is discarded. The solid material A112 mainly composed of silicon particles obtained by filtration contains oil (0.1 wt% to 10 wt% of the silicon particles) and a small amount of water. The solid matter A112 obtained by centrifugation and the solid matter A112 obtained by filtration can proceed in the same way to the next step (drying) as shown in the flowchart of FIG. .

  As shown in the flowchart of FIG. 1, the solid material A 112 is dried in a drying furnace 114. The purpose of drying is to remove a small amount of water contained in the solid material A112. Therefore, the temperature of the drying furnace 114 is preferably 100 ° C to 120 ° C. At this temperature, water evaporates but oil does not evaporate. The components of the solid B115 after drying are silicon particles and oil (0.1 wt% to 10 wt% of the silicon particles).

  According to the experiment by the present inventor, by adjusting the rotation speed and the rotation time of the centrifuge 106, the solid B115 has 0.1% by weight to 10% by weight (typically 3% by weight) of the silicon particles. %) Oil can be included. Alternatively, by adjusting the molecular pore size of the filter 110 and the filtration pressure, the solid substance B115 contains 0.1 wt% to 10 wt% (typically 3 wt%) of oil. be able to.

  The surface of the silicon particles in the solid material B115 is considered to include a portion where silicon is exposed and a portion where silicon is covered with oil. It is considered that the portion where the silicon is exposed reacts with the alkaline aqueous solution, and the portion where the silicon is covered with oil does not react with the alkaline aqueous solution. If the entire surface of the silicon particles is covered with oil, it is considered that the reaction between the silicon particles and the aqueous alkali solution does not occur. When the silicon exposed surface and the part covered with oil are mixed in an appropriate ratio on the surface of the silicon particle, the silicon particle and the alkaline aqueous solution react slowly, and the silicon particle and the alkaline aqueous solution stay for a long time. It is believed that the reaction can continue and hydrogen gas can be generated constantly.

  Water 116 is added to the solid B 115 obtained by drying in the drying furnace 114 to obtain sludge A117. In order to distinguish sludge obtained by adding water 116 to solid B115 and sludge obtained by adding reaction inhibitor 121 and water 123 to solid C in a later step, water is added to solid B115. The sludge obtained by adding 116 is named sludge A117, and the sludge obtained by adding the reaction inhibitor 121 and water 123 to the solid C is named sludge B124. Sludge A117 is the silicon raw material A for hydrogen gas production of the present invention. The reason why water 116 is added to the solid material B115 to make the sludge A117 is to first make it suitable for pumping with a sludge pump. Secondly, the reaction heat between the silicon particles and the aqueous alkali solution is cooled with water. Third, to replenish water consumed by the reaction. The amount of water 116 added is preferably 1 to 10 times the weight of the silicon particles contained in the solid B115, more preferably 1 to 5 times, and even more preferably 2 to 4 times. When the water 116 is added 1 to 10 times, the silicon particles are uniformly dispersed in the water 116, so that clogging of pipes and pumps is less likely to occur.

  According to the study of the present inventor, the silicon raw material A for hydrogen gas production (sludge A117) is 0.1 wt% to 10 wt%, preferably 0.5 wt% to 5 wt%, more preferably 2 wt% of silicon particles. When the oil content of 4% by weight to 4% by weight, typically 3% by weight, is mixed, the silicon particles and the aqueous alkali solution continue to react for a long time, and hydrogen gas can be generated constantly.

  Even if the silicon particles in the silicon raw material A for hydrogen gas production (sludge A117) are well dispersed, the silicon particles may settle if left standing for a long time. Therefore, it is preferable to redisperse the silicon particles with a dispersing device immediately before injection into the reaction vessel.

  When it is desired to include a reaction-inhibiting substance different from the oil, or when it is desired to control the amount of the reaction-inhibiting substance more precisely, the next step of the flowchart of FIG. 1 is further performed. As shown in the flowchart of FIG. 1, the solid B115 containing oil is fired in a high-temperature furnace 118, and the oil 119 derived from the coolant is evaporated to obtain a solid C120 made of only silicon particles. The temperature of the high temperature furnace 118 is preferably 500 ° C to 700 ° C, and more preferably 600 ° C. The oil component 119 evaporates at this temperature. Nitrogen gas is passed through the high temperature furnace 118 to prevent surface oxidation of the silicon particles and oxidation and combustion of the oil component 119.

  The solid C120 baked in the high temperature furnace 118 contains almost no oil. Therefore, the solid substance C120 is mixed with the reaction inhibitor 121 and water 123 to obtain sludge B122. The amount of the reaction inhibitor 121 is 0.1% to 10% by weight of the silicon particles, preferably 0.5% to 5% by weight, more preferably 2% to 4% by weight, typically 3%. %. The reaction inhibiting substance 121 may be the same substance as the oil component 119 or a different substance.

  Examples of the reaction inhibitor to be mixed will be described later, but reaction inhibitors such as carboxylic acids, water-soluble polymers, and monomers are hardly contained in the coolant. Therefore, in particular, when a reaction inhibitor such as a carboxylic acid, a water-soluble polymer, or a monomer is used, a process after firing in the high temperature furnace 118 is necessary.

  Sludge B124 is the silicon raw material B for hydrogen gas production of the present invention. The reason for adding the water 123 is to first mix the silicon particles and the reaction-suppressing substance uniformly and to make it suitable for pumping with a sludge pump. Secondly, the reaction heat between the silicon particles and the aqueous alkali solution is cooled with water. Third, to replenish water consumed by the reaction. The addition amount (weight) of the water 123 is preferably 1 to 10 times, more preferably 1 to 5 times, and further preferably 2 to 4 times the weight of the solid C120 (silicon particles).

  According to the experiment of the present inventor, the sludge A117 containing 3% by weight of oil (propylene glycol) derived from the coolant and 3% by weight of a reaction inhibitor (propylene glycol) of the same kind as the oil are mixed after firing in a high temperature furnace. When the sludge B124 used was used as a silicon raw material for hydrogen gas production, the hydrogen gas generation situation was the same. Therefore, when the oil contained in the coolant 103 is used, it is advantageous to use the sludge A117 having a short manufacturing process. However, when using a reaction-suppressing substance that is not contained as an oil component in the coolant 103, it is necessary to use the sludge B124 produced in the process after the high-temperature furnace 118 in the flowchart of FIG.

As the reaction inhibitor, the following water-soluble organic substances or mixtures thereof are preferred. (1) and (2) may be contained in the coolant as oil. (3) and (4) are usually not included in the coolant, and even if included, the amount is small.
(1) Monohydric alcohol: isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol (2) Polyhydric alcohol: ethylene glycol, diethylene glycol, propylene Glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
(The above monohydric alcohol and polyhydric alcohol can be collectively expressed as X- (OH) n. Here, X is a saturated or unsaturated hydrocarbon group having 3 to 7 carbon atoms, and n is 1 or more. Integer, n <Cm.)
(3) Carboxylic acid / saturated fatty acid: formic acid, lactic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid , Heptadecanoic acid / unsaturated aliphatic carboxylic acid: acrylic acid, oleic acid / hyroxylic acid: malic acid, citric acid / dicarboxylic acid: oxalic acid, maleic acid, fumaric acid (4) water-soluble polymer, monomer vinylpyrrolidone, polyvinylpyrrolidone , Sodium polyacrylate, polyethylene oxide, polyethylene imide, polyvinyl alcohol, polyacrylamide, polyethylene glycol.

  FIG. 2 is a configuration diagram of the hydrogen gas production apparatus 200 of the present invention. A silicon raw material 202 for producing hydrogen gas is injected into a sealed reaction tank 201 by a sludge pump 203. The silicon raw material 202 for producing hydrogen gas is the sludge A117 (silicon raw material A for producing hydrogen gas) or sludge B122 (silicon raw material B for producing hydrogen gas) in the flowchart of FIG. Therefore, as the sludge pump 203, a Mono pump or a gear pump capable of pumping sludge is suitable.

  An alkaline aqueous solution 204 (for example, NaOH aqueous solution) is injected into the reaction tank 201 by an alkaline aqueous solution pump 205. As the alkaline aqueous solution pump 205, for example, an alkali-resistant pump made of fluororesin or polyethylene is suitable. The reaction tank 201 needs to have pressure resistance because hydrogen gas is generated and is in a pressurized state. Further, the reaction vessel 201 needs to be resistant to alkali. Therefore, the reaction vessel 201 is preferably a stainless steel pressure vessel.

  An alkaline aqueous solution 204 and a silicon raw material 202 for producing hydrogen gas are mixed in a reaction vessel 201 to obtain a mixed solution 208. Since the silicon raw material 202 for producing hydrogen gas is sludge (mud), it is difficult to uniformly mix and disperse with the alkaline aqueous solution 204. Therefore, ultrasonic vibration is applied by the ultrasonic vibrator 206 or stirring is performed with a stirring blade (not shown) so that the silicon raw material 202 for producing hydrogen gas and the alkaline aqueous solution 204 are uniformly mixed.

When silicon raw material 202 for hydrogen gas production and alkaline aqueous solution 204 are mixed, Si + 2OH ⁻ + H ₂ O → SiO ₃ ²⁻ + 2H ₂ ↑
Reaction occurs, and hydrogen gas is generated. The generated hydrogen gas accumulates in the internal space of the reaction vessel 201.

  Since the reaction in which the hydrogen gas of the above formula is generated has a slow reaction rate at room temperature, the temperature of the mixed liquid 208 in the reaction tank 201 is raised by the heater 207 before the silicon raw material 202 for producing hydrogen gas is charged. The heater 207 is controlled while measuring the temperature of the mixed liquid 208 with a thermometer 209. The temperature of the mixed liquid 208 is controlled by the heater 207 so as to be 50 ° C. to 90 ° C. (preferably 60 ° C. to 80 ° C.). When the temperature of the mixed liquid 208 is lower than 50 ° C., the reaction rate becomes slow (hydrogen gas generation is reduced). When the temperature of the mixed liquid 208 is higher than 90 ° C., the reaction rate increases (hydrogen gas generation increases), but there is a high possibility that the reaction will run out of heat. In addition, there is less time to deal with when a thermal runaway occurs. Therefore, the temperature of the mixed liquid 208 is suitably 50 ° C to 90 ° C.

  When the reaction heat between the silicon raw material 202 for hydrogen gas production and the alkaline aqueous solution 204 is generated, the heating of the heater 207 is weakened or stopped. If the generation of reaction heat further increases and the temperature of the mixed solution 208 becomes higher than the upper limit even when the heater 207 is turned off, the mixed solution 208 is cooled by the cooler 210. At the same time, the injection of the silicon raw material 202 for producing hydrogen gas is reduced or stopped.

  When an aqueous NaOH solution is used as the alkaline aqueous solution 204, the concentration of the aqueous NaOH solution is preferably 1 mol / L to 8 mol / L, and more preferably 3 mol / L to 4 mol / L. When the concentration of the NaOH aqueous solution exceeds 8 mol / L, the viscosity of the NaOH aqueous solution becomes too high and it becomes difficult to uniformly mix with the silicon raw material 202 for producing hydrogen gas. When the silicon raw material 202 for producing hydrogen gas is injected, sodium metasilicate is formed, so that the viscosity of the mixed solution 208 is further increased and uniform mixing is difficult. If the NaOH aqueous solution and the silicon raw material 202 for producing hydrogen gas are not uniformly mixed, the reaction may be non-uniform. When the concentration of the NaOH aqueous solution is less than 1 mol / L, the hydrogen gas generation reaction may not sufficiently proceed. Therefore, the concentration of the NaOH aqueous solution is preferably 1 mol / L to 8 mol / L.

  In the hydrogen gas production apparatus 200 of the present invention, the silicon raw material A or hydrogen gas for producing hydrogen gas produced according to the flowchart of FIG. 1 is used to solve the second problem (moderately suppressing the reaction between the silicon particles and the aqueous alkali solution). A silicon raw material B for production is used. Since the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production used in the present invention contains a certain amount of oil or a reaction suppressing substance, the silicon particles and the aqueous alkali solution are suppressed from reacting rapidly. However, since the oil or reaction inhibitor is not so much as to inhibit the reaction, it generates a theoretical amount of hydrogen gas. In the hydrogen gas production apparatus 200 of the present invention, since the silicon particles and the aqueous alkaline solution 204 react slowly, the silicon particles and the aqueous alkaline solution 204 can continue to react for a long time, and hydrogen gas can be generated constantly.

  The reason why the pressure fluctuation of the reaction tank is observed in the hydrogen gas production apparatus (see FIG. 6) of Patent Document 2 is considered to be that silicon sludge and an aqueous alkali solution are injected intermittently. In the hydrogen gas production apparatus of Patent Document 2, silicon sludge and an aqueous alkaline solution react rapidly. Therefore, it becomes impossible to inject silicon sludge and aqueous alkali solution continuously, and it seems to inject intermittently.

  In order to solve the third problem (reaction tank pressure fluctuation), the hydrogen gas production apparatus 200 of the present invention continuously injects the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas in principle. (Since the silicon raw material 202 for producing hydrogen gas used in the hydrogen gas producing apparatus 200 of the present invention does not react rapidly, the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas can be injected continuously.) Alkali By continuously injecting the aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas, the hydrogen gas can be obtained stably and continuously. However, the injection rates of the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas are not always constant. This is because even if the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas are injected at a constant rate, the hydrogen gas generation rate may not be constant.

  In the hydrogen gas production apparatus 200 of the present invention, the injection rate of the alkaline aqueous solution 204 is such that the alkali concentration of the mixed solution 208 in the reaction vessel 201 is a predetermined value (1 mol / L to 8 mol / L when using an aqueous NaOH solution, preferably 3 mol / L to 4 mol / L). In order to adjust the alkali concentration of the mixed solution 208 to a predetermined value, the alkali concentration is measured and the change rate (time differentiation) of the alkali concentration is calculated, and the injection rate of the alkaline aqueous solution 204 is feedback-controlled. The alkali concentration of the mixed liquid 208 is measured by titrating the liquid sampled from the neutralization titration sampling terminal 211 with a neutralization titration apparatus (not shown). Depending on the control result, the injection of the alkaline aqueous solution 204 may be interrupted.

In the reaction tank 201, SiO ₂ (OH) ₂ ²⁻ of the reaction formula (4) is accumulated. This hydrate (SiO ₂ (OH) ₂ ²⁻ ) is so-called water glass and has a pH buffering action. Therefore, even if the pH of the mixed solution 208 is measured, the alkali concentration cannot be accurately known. Therefore, instead of the pH of the liquid mixture 208, the sample of the liquid mixture 208 is titrated to measure the alkali concentration.

  Further, the injection rate of the silicon raw material 202 for producing hydrogen gas is controlled so that the temperature of the mixed solution 208 in the reaction vessel 201 becomes a predetermined value (50 ° C. to 90 ° C., preferably 60 ° C. to 80 ° C.). . In order to set the temperature of the mixed liquid 208 to a predetermined value, the temperature is measured with a thermometer 209 and the rate of change (time differentiation) of the temperature is calculated to determine the injection rate of the silicon raw material 202 for producing hydrogen gas. Feedback control. Depending on the control result, the injection of the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas may be interrupted. Furthermore, the liquid mixture 208 may be cooled by the cooler 210.

  The temperature of the mixed liquid 208 rises due to the heat of reaction. On the other hand, the temperature of the mixed solution 208 is lowered by the injection of the alkaline aqueous solution 204 and the injection of the silicon raw material 202 for producing hydrogen gas (because the temperature of the alkaline aqueous solution 204 and the silicon raw material 202 for producing hydrogen gas is lower than the mixed solution 208. Is). In order to suppress the temperature rise of the mixed solution 208 due to reaction heat by the injection of the alkaline aqueous solution 204 and the injection of the silicon raw material 202 for hydrogen gas production, the alkaline aqueous solution 204 and the silicon raw material 202 for hydrogen gas production before the injection are kept at about 20 ° C. It is desirable to keep it in

  Thus, by controlling the injection rate of the alkaline aqueous solution 204 and the silicon raw material 202 for hydrogen gas production based on the alkali concentration and temperature of the mixed solution 208, the hydrogen gas generation rate can be made constant. Depending on the control result, the injection of the silicon raw material 202 for producing hydrogen gas may be interrupted.

  In the conventional hydrogen gas production apparatus, the hydrogen gas generated in the reaction tank is led to a condenser. In the hydrogen gas production apparatus 200 of the present invention, a scrubber 214 is provided between the reaction vessel 201 and the condenser 213 in order to solve the fourth problem (clogging with alkaline aqueous solution mist and silicon particles). Hydrogen gas generated in the reaction vessel 201 is guided to the scrubber 214. The scrubber 214 can remove the alkaline aqueous solution mist, metasilicate hydrate, and silicon particles scattered from the reaction vessel 201 before entering the condenser 213.

  In the scrubber 214, although not shown, a chemical-resistant (for example, vinyl chloride) processing container is filled with a large number of chemical-resistant fillers (for example, small ridges made of polyethylene) having a high clearance ratio. A treatment liquid (in the case of the present invention, water or an acid aqueous solution, preferably dilute sulfuric acid) is sprinkled from the upper part of the treatment container to the entire packing, and a gas to be treated is caused to flow from the lower part of the treatment container. In the hydrogen gas production apparatus 200 of the present invention, the gas to be treated (gas P) includes hydrogen gas, water vapor, alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles. The gas P reacts with the processing liquid while passing through the gaps in the packing. The alkaline aqueous solution mist is neutralized or dissolved by the treatment liquid. The metasilicate hydrate mist and silicon particles are washed away by the treatment liquid. As a result, the gas Q that has passed through the scrubber 214 contains hydrogen gas and water vapor, but does not contain alkaline aqueous solution mist, metasilicate hydrate mist, or silicon particles. Thereby, since the gas Q (hydrogen gas and water vapor) is obtained, the clogging of the condenser 213 can be eliminated.

  Since the gas Q that has passed through the scrubber 214 is a mixture of hydrogen gas and water vapor, the water Q is removed through the condenser 213. In the condenser 213, the gas Q is cooled by, for example, cooling water, and water vapor is condensed to remove moisture. The hydrogen gas processed by the condenser 213 contains almost no moisture. The dew point temperature of the condenser 213 is determined according to the specifications of the hydrogen gas supply destination.

  A back pressure regulator 215 is installed on the outlet side of the condenser to regulate the pressure from the reaction tank 201 to the condenser 213. The pressure in the reaction vessel 201 is measured with a pressure gauge 212. This regulation pressure is preferably 0.05 MPa to 0.5 MPa, more preferably 0.05 MPa to 0.15 MPa. When hydrogen gas is generated above the regulation pressure, the hydrogen gas is sent to the compressor 216, compressed and pressurized, and stored in the cylinder 217. The pressurization by the compressor 216 depends on the standard of the cylinder 217, but is 35 MPa or 70 MPa in the case of a hydrogen station of a fuel cell vehicle (FCV).

  In the hydrogen gas production apparatus 200 of the present invention, since the purity of the hydrogen gas processed in the condenser 213 is high (for example, 99.9%), it can be used as it is depending on the application. When used for such an application, the hydrogen gas processed in the condenser 213 is packed in the cylinder 217 through the compressor 216, and becomes hydrogen gas as a product.

  When higher purity hydrogen gas is required, the hydrogen gas is passed through a hydrogen gas purifier 218 for processing. The hydrogen gas purification device 218 is, for example, a palladium alloy film. Since the palladium alloy film does not pass a gas other than hydrogen gas (for example, nitrogen gas, oxygen gas, or rare gas), the hydrogen gas that has passed through the palladium alloy film becomes a high-purity hydrogen gas. The high-purity hydrogen gas is converted into high-pressure high-purity hydrogen gas by the compressor 216 and packed in the cylinder 217, and becomes high-purity hydrogen gas as a product.

In the reaction tank 201, SiO ₂ (OH) ₂ ²⁻ of the reaction formula (4) is accumulated. When H ₂ O is subtracted from this, it becomes SiO ₃ ²⁻ , which is a metasilicate ion. This hydrate (SiO ₂ (OH) ₂ ²⁻ ) is so-called water glass. Water glass exhibits strong alkalinity by hydrolysis and has a pH buffering action. When hydrate (SiO ₂ (OH) ₂ ²⁻ ) accumulates to some extent in the reaction tank 201, it is necessary to remove the hydrate (SiO ₂ (OH) ₂ ²⁻ ). The concentration of hydrate (SiO ₂ (OH) ₂ ²⁻ ) can be measured simultaneously with the neutralization titration described above. To what extent the concentration of the hydrate (SiO ₂ (OH) ₂ ²⁻ ) should be continued is determined by comprehensively considering the cost of hydrogen gas production and the like.

If it is determined that the hydrogen gas generation amount is reduced due to accumulation of hydrate (SiO ₂ (OH) ₂ ²⁻ ) in view of the cumulative injection amount of the silicon raw material 202 for hydrogen gas production and the cumulative generation amount of hydrogen gas, The injection of the silicon raw material 202 for gas production is stopped. After confirming that all of the silicon raw material 202 for producing hydrogen gas in the reaction vessel 201 has reacted, the mixed solution 208 containing the hydrate (SiO ₂ (OH) ₂ ²⁻ ) is taken out from the reaction vessel 201 and then the reaction vessel. 201 is cleaned.

[Production of silicon raw material A for hydrogen gas production]
As a coolant, a mixed solution of 90% by weight of water and 10% by weight of propylene glycol was used. Using this coolant, a silicon ingot was cut with a multi-wire saw to produce a silicon wafer. Chips contained in the waste coolant were silicon particles having an average particle diameter of 1 μm. The waste coolant was centrifuged with a centrifuge A (2500 rpm).

  Next, the silicon waste was centrifuged with a centrifugal separator B (3000 rpm) to obtain a solid A, and the solid A was further dried in a drying furnace at 105 ° C. to obtain a solid B. The composition of the solid B was 97% by weight of silicon particles and 3% by weight of propylene glycol. Thus, by adjusting the amount of oil contained in the coolant 103 as the starting material and the rotation speed of the centrifugal separator B, the amount of oil contained in the solid B is set to a desired value (0.1% by weight of silicon particles). Any value in the range of 10 wt% to 10 wt%.

  FIG. 3 shows the effect of the oil or reaction inhibitor in the hydrogen gas production experiment. In the upper graph of FIG. 3, the horizontal axis represents time, and the vertical axis represents hydrogen gas generation amount (cumulative). In the lower graph of FIG. 3, the horizontal axis represents time, and the vertical axis represents the temperature of the mixture of silicon particles and an aqueous alkali solution. In the upper and lower graphs of FIG. 3, the curve A shows sludge obtained by mixing pure (not containing oil or reaction inhibitor) silicon particles (1.2 g) and 17 g of pure water with a 3.4 mol / L NaOH aqueous solution (1 .2 liters) is a graph in the case of injecting into a reaction tank (2 liters) containing 5 liters with a syringe for 5 seconds. As the silicon particles that do not contain an oil or a reaction inhibitor, a solid C120 (aggregate of silicon particles) from which oil has been removed through a high-temperature furnace 118 shown in the flowchart of FIG.

  In the upper and lower graphs of FIG. 3, curve B shows a silicon raw material for producing hydrogen gas containing 3% by weight of oil and silicon particles (1.2 g) and 17 g of pure water mixed with a 3.4 mol / L NaOH aqueous solution ( It is a graph at the time of inject | pouring into a reaction tank (2 liter) containing 1.2 liters) over 5 seconds with the syringe. The silicon raw material for producing hydrogen gas containing 3% by weight of oil corresponds to sludge A117 in the flowchart of FIG. The oil is propylene glycol.

  In the case of sludge in which pure silicon particles and water were mixed (curve A), the reaction between the silicon particles and the NaOH aqueous solution occurred explosively immediately after mixing and was completed in 43 seconds. Generation of hydrogen gas is not observed after 43 seconds. The maximum generation rate of hydrogen gas (slope of curve A) was 11 liters / minute. Such a reaction that explosively generates hydrogen gas cannot be controlled, and it is difficult to obtain hydrogen gas constantly. Therefore, silicon particles that are not mixed with oil or a reaction inhibitor cannot be used for hydrogen gas production even if they are mixed with water to form sludge.

  In the case of a silicon raw material for producing hydrogen gas containing 3% by weight of oil (curve B), the reaction between the silicon particles and the aqueous NaOH solution is much slower than that of pure silicon particles and water sludge (curve A). As can be seen from the upper graph in FIG. 3, the amount of accumulated hydrogen gas obtained from sludge of pure silicon particles and water (curve A) and the silicon raw material for producing hydrogen gas (curve B) containing 3% by weight of oil are obtained. The amount of accumulated hydrogen gas is the same. That is, the silicon raw material for producing hydrogen gas containing 3% by weight of oil (curve B) generates hydrogen gas as the theoretical value although reaction is slow. However, the reaction time of pure silicon particles and water sludge (curve A) is about 30 seconds, whereas the reaction time of silicon raw material for hydrogen gas production (curve B) containing 3% by weight of oil is about 800 seconds. It is. Therefore, by including 3% by weight of oil, the reaction rate becomes about 1/27. Such a mild reaction can be controlled.

  In the lower graph of FIG. 3, the temperature change of the mixed solution of silicon particles and alkaline aqueous solution shows that in the case of pure silicon particles (curve A), the temperature of the mixed solution decreases by 0.7 ° C. immediately after silicon particle injection. However, it rose 2.7 ° C immediately. The reason why the temperature decreased by 0.7 ° C first is that the sludge was at room temperature. The reason why the temperature rose by 2.7 ° C. is that the mixed solution was heated by the reaction heat. In the case of silicon particles mixed with 3% by weight of oil (curve B), the temperature change of the mixed solution is within 1 ° C. throughout the reaction. This is because the reaction is slow and the amount of heat of reaction generated per hour is small.

  FIG. 4 (Example 1) shows a silicon raw material A for hydrogen gas production in which silicon particles, 3% by weight of oil (propylene glycol) of silicon particles, and pure water having a weight three times that of silicon particles are mixed. It is a graph which shows the amount of hydrogen gas generation | occurrence | production when it inject | pours continuously for 221 seconds with a Mono pump to the reaction tank (2 liter) containing NaOH solution (1.2 liter) of .4 mol / L, and the temperature of a liquid mixture. . The horizontal axis of the graph is time, the left vertical axis is hydrogen gas amount (cumulative), and the right vertical axis is temperature. The injection amount of silicon particles is 4.8 g / min.

  During the injection of the silicon raw material A for producing hydrogen gas, the amount of accumulated hydrogen gas increased almost in proportion to the time, and the maximum hydrogen gas generation rate was 3 liters / minute. The injection of the silicon raw material A for producing hydrogen gas was stopped in 221 seconds, but the hydrogen gas continued to be generated after that, and the generation has not been completed even after 1500 seconds. The amount of hydrogen gas generated after the injection of the silicon raw material A for producing hydrogen gas was more than three times the amount of hydrogen gas generated during the injection of the silicon raw material A for producing hydrogen gas.

  During the injection of the silicon raw material A for producing hydrogen gas, the temperature of the mixed liquid also increased in proportion to the time. The injection of the silicon raw material A for producing hydrogen gas was stopped in 221 seconds, but after that, the temperature rose with the same slope, rose 8.6 ° C., and then slowly dropped. However, the temperature has not yet returned to the pre-reaction temperature in 1500 seconds. These reasons are considered to be because the injection amount of the silicon raw material A for producing hydrogen gas is too much as compared with the capacity of the reaction vessel. Even if oil is contained in this way, it is difficult to produce hydrogen gas continuously and stably if the injection amount of silicon raw material A for hydrogen gas production is too large compared to the capacity of the reaction vessel. However, because it contains oil, explosive reactions are suppressed.

  FIG. 5 (Example 2) shows a silicon raw material A for hydrogen gas production in which silicon particles, 3% by weight of oil (propylene glycol) of silicon particles, and pure water 3 times the weight of silicon particles are mixed. A graph showing the amount of hydrogen gas generated and the temperature change of the mixture when continuously injected into a reaction tank (2 liters) containing a 4 mol / L NaOH aqueous solution (1.2 liters) with a Mono pump for 857 seconds. is there. The horizontal axis of the graph is time, the left vertical axis is hydrogen gas amount (cumulative), and the right vertical axis is temperature. The injection amount of silicon particles is 1.3 g / min.

  The amount of hydrogen gas generated (cumulative) increases in proportion to the time during the injection of the silicon raw material A for hydrogen gas production, and the generation rate (gradient of the graph) after the injection of the silicon raw material A for hydrogen gas production is stopped. Be gentle. The maximum hydrogen gas generation rate during the injection of the silicon raw material A for hydrogen gas production was 1.2 liters / minute. The amount of hydrogen gas generated after the injection of the silicon raw material A for producing hydrogen gas was about ½ of the amount of hydrogen gas generated during the injection of sludge.

  During the injection of the silicon raw material A for hydrogen gas production, the temperature of the mixed liquid rises almost in proportion to time, and when the injection of the silicon raw material A for hydrogen gas production is stopped, the temperature of the mixed liquid gradually decreases, The temperature returned to the pre-reaction temperature around 1400 seconds. The maximum temperature increase was only 2.2 ° C. The cause of the temperature rise of the liquid mixture was reaction heat, not heating by a heater. From the graph of temperature change, it is estimated that the injection amount of the silicon raw material A for producing hydrogen gas is almost matched to the capacity of the reaction vessel. Thus, if the injection amount of the silicon raw material A for hydrogen gas production is appropriate for the capacity of the reaction vessel, the hydrogen gas can be produced continuously and stably.

  The above description relates to a silicon raw material for producing hydrogen gas produced from silicon scrap generated in a multi-wire saw. However, silicon scrap generated by dicer cutting, lapping, etc. can be used as a silicon raw material for hydrogen gas production by appropriately changing the flowchart of FIG. Dicer cutting does not contain oil because pure water is used instead of coolant. Therefore, silicon scrap generated by dicer cutting can be centrifuged and dried, and then mixed with an appropriate reaction-suppressing substance to obtain a silicon raw material for producing hydrogen gas. In lapping, coolant (including oil) and abrasive grains are mixed with silicon scraps. After removing the abrasive grains, silicon raw materials for hydrogen gas production are processed in the same way as silicon scraps generated by a multi-wire saw. Can do.

  For the measurement of the average particle size of the silicon particles, a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd.) based on the measurement principle of Mie scattering theory was used.

  A large amount of silicon waste is generated during the manufacturing process of the silicon wafer. Conventionally, silicon scrap has been discarded, but the cost burden and environmental burden due to disposal cannot be ignored. According to the present invention, hydrogen gas can be obtained constantly from silicon waste, and silicon waste that has been discarded can be used.

101 Multi-wire saw 102 Silicon ingot 103 Coolant 104 Silicon wafer 105 Waste coolant 106 Centrifuge A
107 Regenerated coolant 108 Silicon waste 109 Centrifuge B
110 Filter 111 Supernatant 112 Solid A
113 Filtrate 114 Drying furnace 115 Solid matter B
116 Water 117 Sludge A
118 High Temperature Furnace 119 Oil 120 Solid C
121 Reaction inhibitor 122 Sludge B
123 Water 200 Hydrogen gas production apparatus 201 Reaction tank 202 Silicon raw material 203 for hydrogen gas production Sludge pump 204 Alkaline aqueous solution 205 Alkaline aqueous solution pump 206 Ultrasonic vibrator 207 Heater 208 Liquid mixture 209 Thermometer 210 Cooler 211 Sampling terminal for neutralization titration 212 Pressure gauge 213 Condenser 214 Scrubber 215 Back pressure regulator 216 Compressor 217 Cylinder 218 Hydrogen gas purification device

Claims (23)

  Silicon raw material A for hydrogen gas production containing silicon particles, 0.1 wt% to 10 wt% oil of the silicon particles, and water. The oil content is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
The silicon raw material A for hydrogen gas production according to claim 1, which is any one of these or a mixture thereof.   The silicon raw material A for hydrogen gas production according to claim 1 or 2, wherein an average particle size of the silicon particles is 0.1 µm to 30 µm.   The silicon raw material A for hydrogen gas production according to any one of claims 1 to 3, wherein the weight of the water is 1 to 10 times the weight of the silicon particles.   A silicon raw material B for producing hydrogen gas containing silicon particles, 0.1 wt% to 10 wt% of a reaction suppressing substance of the silicon particles, and water. The reaction inhibitor is
Formic acid, lactic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, acrylic acid, oleic acid , Malic acid, citric acid, oxalic acid, maleic acid, fumaric acid,
Vinyl pyrrolidone, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene oxide, polyethylene imide, polyvinyl alcohol, polyacrylamide, polyethylene glycol,
The silicon raw material B for hydrogen gas production according to claim 5, which is any one of these or a mixture thereof.   The silicon raw material B for hydrogen gas production according to claim 5 or 6, wherein the silicon particles have an average particle size of 0.1 to 30 µm.   The silicon raw material B for hydrogen gas production according to any one of claims 5 to 7, wherein the weight of the water is 1 to 10 times the weight of the silicon particles. Preparing silicon scraps containing oil and water derived from silicon particles and coolant,
Centrifuge or filter the silicon debris to produce a solid A containing the silicon particles, the oil content of 0.1 wt% to 10 wt% of the silicon particles, and a small amount of the water;
Drying the solid A to produce the solid B containing the silicon particles and 0.1 wt% to 10 wt% of the oil content of the silicon particles;
The manufacturing method of the silicon raw material A for hydrogen gas manufacture including the process of adding water to the said solid substance B and manufacturing the sludge A. The oil content is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
The method for producing a silicon raw material A for producing hydrogen gas according to claim 9, which is any one of these or a mixture thereof.   The method for producing a silicon raw material A for hydrogen gas production according to claim 9 or 10, wherein the drying temperature of the solid A is 100 ° C to 120 ° C. Preparing silicon scraps containing oil and water derived from silicon particles and coolant,
Centrifuge or filter the silicon waste to produce a solid A containing the silicon particles, the oil and a small amount of the water,
Drying the solid A to produce a solid B containing the silicon particles and the oil;
A step of producing a solid C comprising silicon particles by drying the solid B at a high temperature to evaporate the oil;
A method for producing a silicon raw material B for producing hydrogen gas, comprising the step of producing sludge B by adding 0.1 wt% to 10 wt% of a reaction inhibiting substance of the silicon particles and water to the solid C. The reaction inhibitor is
Isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-ethyl-1-hexanol,
Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol,
Formic acid, lactic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, acrylic acid, oleic acid , Malic acid, citric acid, oxalic acid, maleic acid, fumaric acid,
Vinyl pyrrolidone, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene oxide, polyethylene imide, polyvinyl alcohol, polyacrylamide, polyethylene glycol,
The method for producing a silicon raw material B for producing hydrogen gas according to claim 12, which is any one of these or a mixture thereof.   The method for producing a silicon raw material B for producing hydrogen gas according to claim 12 or 13, wherein the drying temperature of the solid A is 100 ° C to 120 ° C.   The method for producing a silicon raw material B for producing hydrogen gas according to any one of claims 12 to 14, wherein the high temperature drying temperature of the solid B is 500C to 700C. Preparing a silicon raw material A for hydrogen gas production according to any one of claims 1 to 4 or a silicon raw material B for hydrogen gas production according to any one of claims 5 to 8,
Preparing an alkaline aqueous solution,
Injecting the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production into the reaction vessel while feedback controlling the injection rate based on the temperature of the mixed liquid in the reaction vessel;
Injecting the alkaline aqueous solution into the reaction vessel while feedback controlling the injection rate based on the alkali concentration in the reaction vessel;
Maintaining a mixture of the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production and the alkaline aqueous solution in the reaction vessel at a predetermined temperature;
The gas P containing hydrogen gas, water vapor, alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles taken out from the reaction vessel is treated with a scrubber, and the alkaline aqueous solution mist and the metasilicate are obtained from the gas P. Salt hydrate mist, removing the silicon particles,
A method for producing hydrogen gas, comprising: treating the gas Q containing the hydrogen gas and the water vapor treated with the scrubber with a condenser to remove the water vapor from the gas Q.   The method for producing hydrogen gas according to claim 16, wherein the alkaline aqueous solution is an aqueous NaOH solution or an aqueous KOH solution.   The method for producing hydrogen gas according to claim 17, wherein the concentration of the NaOH aqueous solution or the KOH aqueous solution is 1 mol / L to 8 mol / L.   The method for producing hydrogen gas according to any one of claims 16 to 18, wherein the predetermined temperature is 50C to 90C. A sealable reaction vessel;
Means for supplying the silicon raw material A for producing hydrogen gas according to any one of claims 1 to 4 or the silicon raw material B for producing hydrogen gas according to any one of claims 5 to 8 to the reaction vessel;
Means for supplying an alkaline aqueous solution to the reaction vessel;
A thermometer, a heater and a cooler provided in the reaction vessel;
A hydrogen gas production apparatus comprising a scrubber, a condenser, and a regulator in this order on the hydrogen gas extraction side of the reaction tank.   21. The hydrogen gas production apparatus according to claim 20, wherein the scrubber removes alkaline aqueous solution mist, metasilicate hydrate mist, and silicon particles generated from the reaction vessel.   The hydrogen gas production apparatus according to claim 20 or 21, wherein the means for supplying the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production is a Mono pump or a gear pump.   The hydrogen gas production apparatus according to any one of claims 20 to 22, wherein the reaction vessel includes means for mixing the silicon raw material A for hydrogen gas production or the silicon raw material B for hydrogen gas production and the alkaline aqueous solution.

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