Method for repairing and regenerating iron phosphate in lithium extraction residue

Abstract

The application discloses a method for repairing and regenerating iron phosphate in lithium extraction residue, and particularly relates to the technical field of lithium iron phosphate battery recycling, and comprises the following steps: carrying out an oxidation film etching and washing on the lithium extraction residue, removing aluminum, and performing a combined process of defluorination-decarbonization-crystal transformation, so that the orthorhombic iron phosphate is converted into high-value triagonal iron phosphate, and the method has the characteristics of high yield, low cost and short process, effectively solves the technical problems of long process, high cost, low yield of iron phosphate and serious physical property damage in the traditional wet recovery process, and has wide industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium iron phosphate battery recycling, and particularly relates to a method for repairing and regenerating iron phosphate in lithium extraction residue. BACKGROUND

[0002] Lithium iron phosphate batteries have been widely used in pure electric vehicles, electrochemical energy storage and other fields due to their high safety, long cycle life and low cost. During the production of lithium ion batteries, unqualified intermediate products are generated, especially during the coating, sheet making and assembly processes before the electrolyte is injected. The positive electrode, separator and negative electrode are easily separated and classified, so the positive electrode sheet powder can be recovered from the waste positive electrode material and waste positive electrode sheet.

[0003] The positive electrode sheet powder of the lithium iron phosphate battery without electrolyte injection mainly contains lithium iron phosphate positive electrode material, and also contains a small amount of aluminum, binder and conductive carbon material. Further, since the lithium iron phosphate positive electrode material is not in contact with the electrolyte and has not undergone the charging and discharging process, its physical and chemical properties remain in the initial state, so it has high recycling value.

[0004] However, the current recovery process of lithium iron phosphate battery black powder mainly uses a unified wet process, that is, lithium is leached by acid and oxidizing agent, which leads to the dissolution and leaching of iron, phosphorus and aluminum, and the structure, morphology, particle size and specific surface area of iron phosphate are fundamentally changed. On the one hand, although most of the lithium is leached and enriched in the lithium leaching solution, a large amount of impurities such as iron, phosphorus and aluminum also enter the lithium leaching solution, which not only increases the cost of impurity removal, but also causes a large loss of lithium during the impurity removal process, further increasing the cost. On the other hand, the physical and chemical properties of the iron phosphate in the lithium extraction residue are fundamentally changed, so that its recovery usually requires full dissolution with strong acid, solution impurity removal and recrystallization, which not only consumes a large amount of acid and has high energy consumption, but also lacks technical and economic efficiency.

[0005] Therefore, it is urgent to develop a high-yield, short-process and low-cost direct repair and regeneration technology for lithium extraction residue to maximize the recycling value of the positive electrode sheet powder of the lithium iron phosphate battery without electrolyte injection. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for directly repairing and regenerating lithium extraction residue obtained after chlorination and lithium extraction of positive electrode sheet powder of lithium iron phosphate battery without electrolyte injection. The core is to remove aluminum, remove fluorine and remove carbon and convert crystals from the lithium extraction residue, which has the characteristics of high yield, short process and low cost.

[0007] The specific technical solutions adopted by the present application are as follows:

[0008] The present application provides a method for repairing and regenerating iron phosphate in lithium extraction residue, which comprises:

[0009] The lithium extraction residue is subjected to oxidation film etching, wherein the lithium extraction residue is obtained by gas-solid chlorination and water solution leaching lithium extraction of lithium iron phosphate battery positive pole piece powder without electrolyte injection, and the crystal form of iron phosphate in the lithium extraction residue is orthorhombic; the step specifically comprises: immersing the lithium extraction residue into an etching solution for oxidation film etching to obtain the lithium extraction residue with removed oxidation film, wherein the pH of the etching solution is controlled at 2.5-3.0, the total acid [H + ] of the etching solution is in a molar amount of a, the total aluminum oxide impurity [Al2O3] in the lithium extraction residue is in a molar amount of b, log(a / b) satisfies 3-5, the temperature of the etching solution is 25℃-95℃, the etching time is 12-48 hours, and the gas-solid chlorination refers to selective chlorination lithium extraction reaction of chlorine gas and lithium iron phosphate battery positive pole piece powder, wherein the highest temperature of the gas-solid chlorination reaction is less than 120℃;

[0010] The lithium extraction residue after oxidation film etching is immersed into an aluminum removal solution for aluminum removal; in the step, the pH of the aluminum removal solution is controlled at 1.0-1.6, the total acid of the aluminum removal solution is in a molar amount of c, the total aluminum impurity in the lithium extraction residue is in a molar amount of d, c / d satisfies 3-12, the temperature of the aluminum removal solution is 45℃-95℃, and the aluminum removal time is 10-120 minutes;

[0011] The lithium extraction residue after aluminum removal is loaded into a reactor, first heated to T1 temperature and then defluorination carrier gas is introduced for concentrated deep defluorination to convert the lithium extraction residue into defluorination lithium extraction residue, then heated to T2 temperature and then air or oxygen is introduced for oxidation decarburization to convert the defluorination decarburization lithium extraction residue into orthorhombic iron phosphate, then kept for 2-5 hours for crystal transformation, the orthorhombic iron phosphate is converted into triagonal iron phosphate, and then regenerated iron phosphate is obtained, wherein T1 satisfies 500℃≤T1≤600℃, T2 satisfies 650℃≤T2≤800℃, the defluorination carrier gas is a non-oxidizing gas, the non-oxidizing gas contains a crackable H-containing gas, and the non-oxidizing gas can be mixed with one or more of nitrogen, argon, carbon dioxide and helium; the crackable H-containing gas refers to one or a mixture of more than one of hydrogen, methane, ethane, water vapor, methanol gas, ethanol gas, formic acid gas, acetic acid gas, methyl carbonate gas, methyl ethyl carbonate gas, ethyl carbonate gas and dimethyl carbonate gas.

[0012] Preferably, in the defluorination-decarburization-crystal transformation combined process, absorption purification is further needed, and the tail gas is discharged after reaching the standard, thereby avoiding pollution to the environment.

[0013] The basic principle of the present application is:

[0014] For the lithium extraction residue oxidation film etching process:

[0015] The E-pH diagram of Al (as shown in Figure 2As shown in the figure, at a temperature of 25℃, the stable region of Al2O3 is pH 5.24-6.81, thus, when the pH is less than 3, Al2O3 will gradually be converted into soluble Al 3+ The chemical reaction mechanism of the chemical reaction of the oxidation film etching of the lithium extraction residue is as follows: ;

[0016] Thus, a dense oxidation film on the surface of the metal aluminum is realized, and the dense oxidation film is removed by acid etching;

[0017] For the aluminum removal process of the lithium extraction residue:

[0018] The metal aluminum is dissolved and hydrogen is analyzed in the acid solution, and the chemical reaction mechanism is as follows:

[0019] ;

[0020] At the same time, in the aluminum removal process, the reaction condition is in the dissolution process of Al (i.e., reaction formula (2)); not in the reaction and precipitation process of Al 3+ and PO4 3- :

[0021] ;

[0022] Not in the massive dissolution process of FePO4:

[0023] ;

[0024] Therefore, the occurrence of reaction formula (3) is inhibited, the pH should be <1.8; the progress of reaction formula (4) is delayed, the pH should be >0.5; in combination with the above description, the pH control range of the aluminum removal process is 1.0-1.6, in the pH value range, the dissolution reaction of FePO4 (i.e., reaction formula (4)) is inhibited with the increase of the temperature, and the dissolution reaction of the metal aluminum (reaction formula (2)) is promoted, thus, the reaction temperature needs to be controlled to be 45℃-95℃ of the aluminum removal liquid.

[0025] For the combined process of defluorination-decarbonization-crystal transformation of the lithium extraction residue:

[0026] Under the defluorination temperature T1, by regulating the chemical reaction process, the F contained in the lithium extraction residue is reacted with the H cracked in the carrier gas to generate hydrogen fluoride gas with strong volatility, which quickly escapes with the carrier gas, realizing the effect of efficient and deep removal from the lithium extraction residue, and the chemical reaction formula is as follows: ;

[0027] After the defluorination of the lithium extraction residue, the temperature is increased to T2, and air or oxygen is introduced for oxidation and decarburization, and the chemical reaction mechanism is as follows:

[0028] ;

[0029] After the lithium extraction residue is defluorinated and decarburized for 2-5 hours, the iron phosphate is converted from orthorhombic crystal to trigonal crystal, and then the regenerated iron phosphate is obtained, and the chemical reaction mechanism is as follows:

[0030] .

[0031] Compared with the prior art, the present application has the following beneficial technical effects:

[0032] (1) High yield: In the traditional wet process, the loss of iron and phosphorus mainly comes from two aspects, one is that part of the iron and phosphorus will enter the lithium leaching solution and be removed as impurities in the subsequent purification process; the other is that the liquid phase impurity removal process after the complete acid dissolution of the lithium extraction residue also inevitably causes the loss of iron and phosphorus, and the yield of traditional wet-process iron phosphate is generally 90%; the present application selectively extracts lithium by gas-solid chlorination, and iron, phosphorus and aluminum do not participate in the chlorination reaction, the content of iron and phosphorus in the lithium leaching solution is less than 20 ppm, and the loss can be ignored; the pH value of the present application is controlled in the range of 2.5-3.0 in the oxidation film etching process step, and the solubility of FePO4 in this pH value range is less than 0.01%; the pH value of the aluminum removal process step of the present application is controlled in the range of 1.0-1.6, and the solubility of FePO4 in this pH value range is less than 0.5%; the yield of regenerated iron phosphate of the present application can reach 98.5%.

[0033] (2) Short process: Since the lengthy and complex processes such as complete acid dissolution, impurity removal, recrystallization and decrystallization of iron phosphate in the traditional method are omitted, the main process flow of the present application for repairing and regenerating phosphoric acid iron in lithium extraction residue has only three steps, while the traditional method has more than ten steps, and the process flow of the present application is shortened by nearly 70%.

[0034] (3) Low cost: Compared with the traditional wet process, the present application has the advantage of significantly low cost, and the cost of recovering each ton of phosphoric acid iron is only 30% of that of the traditional wet process, which is mainly because the process flow of the present application is short, which greatly reduces the investment in fixed assets and depreciation; the high yield of iron phosphate further reduces the cost per ton; the present application discards the process route of complete acid dissolution-recrystallization of phosphoric acid iron in lithium extraction residue, and adopts fine acid control and pH value control to remove aluminum and combined process of defluorination-decarburization-crystal transformation based on pyrometallurgy, so as to realize the direct repairing and regeneration of iron phosphate with extremely low acid consumption and energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the description of specific embodiments or prior art. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The process flow chart of the method for repairing and regenerating iron phosphate in the lithium extraction residue provided by the present application is shown in the figure,

[0037] Figure 2 The E-pH diagram of Al under the condition of temperature 25℃, aluminum ion concentration 10 -7 M. Figure 3 The X-ray diffraction analysis spectrum of the regenerated iron phosphate obtained in Example 1 is shown in the figure. DETAILED DESCRIPTION

[0038] The "ranges" disclosed herein are defined by the form of the lower and upper limit, and the given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this manner can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the resin range "a-b" represents a shorthand notation for any real number combination between a and b, where a and b are both real numbers. For example, the resin range "0-5" represents that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these resin combinations. In addition, when it is stated that a parameter is ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, the terms "comprise" and "include" mentioned in this application represent open-ended, and can also be closed-ended. For example, the terms "comprise" and "include" can represent that other components not listed can also be included, or only the listed components can be included.

[0040] The present application will be described in detail below in conjunction with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form.

[0041] Example 1

[0042] A direct repairing and regenerating method for iron phosphate in a lithium extraction residue, the process flow is shown in the figure, Figure 1 The specific process steps are as follows:

[0043] ① Oxidation film etching process

[0044] First, the lithium extraction residue with a dry mass of 100 kg is immersed in the etching solution. The lithium extraction residue is obtained by gas-solid chlorination and water solution leaching of the positive electrode sheet powder of lithium iron phosphate battery without electrolyte injection. The lithium extraction residue contains 0.23% of aluminum by mass, and the total molar amount of aluminum d = 8.52 mol. 0.007% of the aluminum (mainly the surface of the aluminum) is oxidized into an aluminum oxide film, and the total molar amount of the aluminum oxide b = 0.000278 mol. The lithium extraction residue contains 5.23% of the binder PVDF by mass, 4.67% of carbon by mass, and the remaining 89.87% of the lithium extraction residue is orthorhombic iron phosphate. The pH value of the etching solution is controlled at 2.5, the total acid amount of the etching solution and the added hydrochloric acid during the etching process is a = 4.74 mol, and 3 ≤ log(a / b) = 4.23 ≤ 5 is satisfied. The etching temperature is 25°C, and the etching time is 12 hours. After the oxidation film etching of the lithium extraction residue, the lithium extraction residue with the removed oxidation film is obtained.

[0045] ② Aluminum removal process

[0046] The lithium extraction residue with the removed oxidation film obtained in the first step is immersed in the aluminum removal solution. The pH value of the aluminum removal solution is controlled at 1.0, the total acid amount of the aluminum removal solution and the added hydrochloric acid during the aluminum removal process is c = 88.65 mol, and 3 ≤ c / d = 10.4 ≤ 12 is satisfied. The aluminum removal solution temperature is 60°C, and the aluminum removal time is 20 minutes. After the aluminum removal process step, the lithium extraction residue after aluminum removal is obtained.

[0047] ③ Combined defluorination-decarburization-crystal transformation process

[0048] The product obtained in the second step, i.e., the lithium extraction residue after aluminum removal, is loaded into the reactor. First, the temperature is raised to T1 = 500°C, and a defluorination carrier gas is introduced for concentrated deep defluorination. The lithium extraction residue is converted into a defluorinated lithium extraction residue. Then, the temperature is raised to T2 = 650°C, and oxygen is introduced for oxidation. The defluorinated and decarburized lithium extraction residue is converted into orthorhombic iron phosphate. Then, the temperature is kept for 2 hours for crystal transformation. The orthorhombic iron phosphate is converted into triclinic iron phosphate. After the third step of the combined defluorination-decarburization-crystal transformation process, the regenerated iron phosphate is obtained. The defluorination carrier gas is a cleavable H-containing gas containing nitrogen. The cleavable H-containing gas is a mixed gas of hydrogen and methane.

[0049] Example 2

[0050] A direct repair and regeneration method for phosphorus iron in a lithium extraction residue is provided. The process flow is shown in FIG. 1, and the specific process steps are as follows: Figure 1

[0051] ① Oxidation film etching process ​

[0052] First, the lithium extraction residue with a dry mass of 100 kg is immersed in the etching solution. The lithium extraction residue is obtained by gas-solid chlorination and water solution leaching of the positive electrode sheet powder of lithium iron phosphate battery without electrolyte injection. The lithium extraction residue contains 0.23% of aluminum by mass, and the total molar amount of aluminum d=8.52 mol. 0.007% of the aluminum (mainly the surface of the aluminum) is oxidized into an aluminum oxide film, and the total molar amount of the aluminum oxide b=0.000278 mol. The lithium extraction residue contains 5.23% of the binder PVDF by mass, 4.67% of carbon by mass, and the remaining 89.87% of the lithium extraction residue is orthorhombic iron phosphate. The pH value of the etching solution is controlled at 2.7, the total acid amount of the etching solution and the added hydrochloric acid during the etching process is a=1.0 mol, and 3≤log(a / b)=3.56≤5 is satisfied. The etching temperature is 50°C, and the etching time is 24 hours. After the oxidation film etching of the lithium extraction residue, the lithium extraction residue with the oxidation film removed is obtained.

[0053] ②Aluminum removal process

[0054] The lithium extraction residue with the oxidation film removed obtained in the first step is immersed in the aluminum removal solution. The pH value of the aluminum removal solution is controlled at 1.4, the total acid amount of the aluminum removal solution and the added hydrochloric acid during the aluminum removal process is c=88.65 mol, and 3≤c / d=6.27≤12 is satisfied. The aluminum removal solution temperature is 75°C, and the aluminum removal time is 60 minutes. After the aluminum removal process step, the lithium extraction residue after aluminum removal is obtained.

[0055] ③Combined defluorination-decarburization-crystal transformation process

[0056] The product obtained in the second step, i.e., the lithium extraction residue after aluminum removal, is loaded into the reactor. First, the temperature is raised to T1=550°C, and a defluorination carrier gas is introduced for concentrated deep defluorination. The lithium extraction residue is converted into a defluorinated lithium extraction residue. Then, the temperature is raised to T2=750°C, and oxygen is introduced for oxidation. The defluorinated and decarburized lithium extraction residue is converted into orthorhombic iron phosphate. Then, the temperature is kept for 4 hours for crystal transformation. The orthorhombic iron phosphate is converted into triclinic iron phosphate. After the third step of the combined defluorination-decarburization-crystal transformation process, the regenerated iron phosphate is obtained. The defluorination carrier gas is a cleavable H-containing gas containing argon. The cleavable H-containing gas is a mixture of methanol gas and methane.

[0057] Example 3

[0058] A direct repair and regeneration method for phosphorus iron in a lithium extraction residue is provided. The process flow is shown in FIG. 1, and the specific process steps are as follows: Figure 1

[0059] ① Oxidation film etching process

[0060] ​Firstly, the lithium extraction residue with a dry mass of 100 kg is immersed in the etching solution. The lithium extraction residue is obtained by gas-solid chlorination and water solution leaching of the positive electrode tab powder of lithium iron phosphate battery without electrolyte injection. The lithium extraction residue contains 0.23% of aluminum by mass, and the total molar amount of aluminum is d=8.52 mol. 0.007% of the aluminum (mainly the surface of the aluminum) is oxidized into an aluminum oxide film, and the total molar amount of the aluminum oxide is b=0.000278 mol. The lithium extraction residue contains 5.23% of the binder PVDF by mass, 4.67% of carbon by mass, and the remaining 89.87% of the lithium extraction residue is orthorhombic iron phosphate. The pH value of the etching solution is controlled to be 3.0. The total acid amount of the etching solution and the hydrochloric acid added during the etching process is a=0.30 mol, and 3≤log(a / b)=3.03≤5 is satisfied. The etching temperature is 95°C, and the etching time is 48 hours. After the oxidation film of the lithium extraction residue is removed, the lithium extraction residue without the oxidation film is obtained.

[0061] ②Aluminum removal process

[0062] The lithium extraction residue without the oxidation film obtained in the first step is immersed in the aluminum removal solution. The pH value of the aluminum removal solution is controlled to be 1.6. The total acid amount of the aluminum removal solution and the hydrochloric acid added during the aluminum removal process is c=88.65 mol, and 3≤c / d=3.88≤12 is satisfied. The aluminum removal solution temperature is 85°C, and the aluminum removal time is 120 minutes. After the aluminum removal process, the lithium extraction residue after aluminum removal is obtained.

[0063] ③Combined defluorination-decarburization-crystal transformation process

[0064] The lithium extraction residue after aluminum removal obtained in the second step is loaded into the reactor. The temperature is first increased to T1=600°C, and the defluorination carrier gas is introduced to perform concentrated deep defluorination. The lithium extraction residue is converted into the defluorination lithium extraction residue. Then, the temperature is increased to T2=800°C, and oxygen is introduced to perform oxidation. The defluorination-decarburization lithium extraction residue is converted into orthorhombic iron phosphate. Then, the temperature is kept for 5 hours to perform crystal transformation. The orthorhombic iron phosphate is converted into triclinic iron phosphate. After the third step of the combined defluorination-decarburization-crystal transformation process, the regenerated iron phosphate is obtained. The defluorination carrier gas is a cleavable H-containing gas containing carbon dioxide. The cleavable H-containing gas is a mixed gas of ethyl carbonate gas, ethane, and water vapor.

[0065] It should be noted that in Examples 1-3, the acid used in the etching solution and the aluminum removal solution is hydrochloric acid, but it is not limited to hydrochloric acid. It can also be other inorganic acids such as sulfuric acid, nitric acid, etc., or organic acids such as citric acid, malic acid, etc.

[0066] The regenerated iron phosphate obtained in Examples 1-3 is analyzed by X-ray diffraction (XRD), Figure 3The X-ray diffraction spectrum of the regenerated iron phosphate obtained in Example 1 is shown, and the total yield of the regenerated iron phosphate and the impurity content in the regenerated iron phosphate are calculated, and the results are shown in Table 1.

[0067]

[0068] It can be seen from Table 1 and Figure 3 It can be seen from Table 1 and

[0069] The above describes in detail the method for repairing and regenerating iron phosphate in lithium extraction residue provided by the present application. The principles and implementation modes of the present application are described by applying specific examples, and the above description of the examples is only used to help understand the core idea of the present application. It should be pointed out that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for the remediation and regeneration of iron phosphate in lithium extraction residue, characterized in that: The lithium extraction residue was subjected to oxide film etching. The lithium extraction residue was obtained from lithium iron phosphate battery positive electrode powder without electrolyte after gas-solid chlorination and aqueous solution leaching. The iron phosphate in this residue was orthorhombic. Specifically, the lithium extraction residue was immersed in an etching solution for oxide film etching to obtain lithium extraction residue with the oxide film removed. The pH of the etching solution was controlled at 2.5-3.0, and the total acidity of the etching solution [H+] was [not specified]. + Let a be the molar amount of the total alumina impurities [Al2O3] in the lithium extraction slag, and let b be the molar amount of the total alumina impurities [Al2O3] in the lithium extraction slag, satisfying log(a / b)=3-5; The lithium extraction slag after oxide film etching is immersed in aluminum removal solution to remove aluminum. The pH of the aluminum removal solution is controlled at 1.0-1.

6. The total molar amount of acid in the aluminum removal solution is denoted as c, and the total molar amount of metallic aluminum impurities in the lithium extraction slag is denoted as d, satisfying c / d=3-12. The lithium extraction slag after aluminum removal is loaded into a reactor. First, it is heated to temperature T1 and defluorinated carrier gas is introduced for concentrated deep defluorination to convert the lithium extraction slag into defluorinated lithium extraction slag. Then, it is heated to temperature T2 and air or oxygen is introduced for oxidation and decarbonization to convert the defluorinated and decarbonized lithium extraction slag into orthorhombic ferric phosphate. Then, it is kept at this temperature for 2-5 hours to convert the orthorhombic ferric phosphate into trigonal ferric phosphate, thus obtaining regenerated ferric phosphate. Here, T1 satisfies 500℃≤T1≤600℃, and T2 satisfies 650℃≤T2≤800℃.

2. The repair and regeneration method according to claim 1, characterized in that: The temperature of the etching solution is 25℃-95℃, and the etching time is 12-48 hours.

3. The repair and regeneration method according to claim 1, characterized in that: The temperature of the aluminum removal solution is 45℃-95℃, and the aluminum removal time is 20-120 minutes.

4. The repair and regeneration method according to any one of claims 1 to 3, characterized in that: The gas-solid chlorination refers to the selective chlorination and lithium extraction reaction between chlorine gas and lithium iron phosphate battery positive electrode powder, wherein the maximum temperature of the gas-solid chlorination reaction is less than 120°C.

5. The repair and regeneration method according to any one of claims 1 to 3, characterized in that: The defluorination carrier gas is a non-oxidizing gas containing crackable H-containing gases, and is mixed with one or more of nitrogen, argon, carbon dioxide, and helium; the crackable H-containing gases are one or more of the following: methyl methacrylate gas, methyl ethyl methacrylate gas, ethyl carbonate gas, and dimethyl carbonate gas, or a mixture of hydrogen and methane, or a mixture of methanol and methane, or a mixture of ethyl carbonate, ethane, and water vapor.

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