Method for measuring gas generation amount from waste liquid

Abstract

To provide a measuring method to confirm in advance whether or not an amount of gas generated from waste liquid is large enough to cause problems such as tank deformation due to vibration during transport of the waste liquid.SOLUTION: A method for measuring an amount of gas generated when waste liquid is vibrated, includes: introducing gas generated by vibrating, under a prescribed condition, a prescribed amount of a waste liquid sample S loaded in a sampling container 1 into a sealed intermediate container 4 having an effective volume larger than the amount of generated gas and filled with air; and introducing the air expelled from the intermediate container 4 by the introduced gas into a measurement container 7 held upside down in water while still filled with liquid, thereby determining the amount of gas generated from the waste liquid sample S.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the amount of gas generated from waste liquid, and more particularly to a method for easily measuring the amount of gas generated from waste liquid such as used nitric acid or aqua regia placed inside a container by vibrating the container. [Background technology]

[0002] The electronic circuit boards and electronic components used in electronic devices such as smartphones and personal computers contain base metals such as copper and iron, as well as precious metals such as gold, silver, and palladium, and rare metals such as nickel and niobium. Therefore, when these electronic devices are discarded after their useful life is over, a large amount of waste containing valuable precious and rare metals is generated. In addition, valuable metals such as nickel and cobalt are used in the positive electrode material of lithium-ion secondary batteries, which have excellent properties such as high energy density and have seen a rapid increase in demand in recent years. Therefore, when lithium-ion secondary batteries are discarded, a large amount of waste containing valuable metals is also generated.

[0003] In recent years, with increasing environmental awareness, there has been a demand for reusing waste containing valuable metals as recyclable resources, and various technologies have been proposed for this purpose. For example, a hydrometallurgical process has been proposed to recover valuable metals from waste. This process involves crushing the waste, dissolving the target metals using nitric acid, sulfuric acid, hydrochloric acid, aqua regia, or the like, and then subjecting the resulting solution to reduction or solvent extraction to recover the target valuable metals. Patent Document 1 proposes a hydrometallurgical process for recovering valuable metals. In this process, scrap containing precious metals is first immersed in aqua regia to recover a sparingly soluble precious metal residue containing sparingly soluble platinum, and the recovered residue is then heated at a temperature of 600°C or higher for at least three hours, after which it is dissolved in nitric acid, and the remaining undissolved material is dissolved in aqua regia.

[0004] The treatment liquid used to recover valuable metals using the above-mentioned wet treatment method is discharged as waste liquid containing acidic solutions such as nitric acid and aqua regia after use. This waste liquid may be reused as is depending on the conditions, but it is usually outsourced to an external industrial waste disposal company for treatment. 3 The waste liquid is placed in a so-called 1 cubic meter tank and transported by truck, etc. During transportation, vibrations and other factors can cause the waste liquid inside the 1 cubic meter tank to foam, which can cause problems such as the gas filling the gas phase inside the 1 cubic meter tank and deforming the 1 cubic meter tank or the waste liquid spilling out of the 1 cubic meter tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-041047 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the above-mentioned problems caused by gases generated from waste liquids due to vibrations during transportation only occur once or twice every few years, it is desirable to prevent such problems as much as possible, considering the cost of damaging equipment and the adverse impact on the environment, etc. Therefore, before transporting waste liquids such as nitric acid or aqua regia in a 1 cubic meter tank, it is necessary to estimate in advance, preferably at the work site, whether or not the vibrations of the waste liquid will generate an amount of gas that will cause problems such as deformation of the 1 cubic meter tank or spillage of the waste liquid from the 1 cubic meter tank.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a measurement method for determining whether or not a quantity (volume) of gas is generated from waste liquid that is large enough to cause problems such as tank deformation due to vibrations during transportation, preferably at the work site, in order to determine whether or not the waste liquid can be handed over to an industrial waste disposal company. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the method for measuring the amount of gas generated according to the present invention is a method for measuring the amount of gas generated when waste liquid is vibrated, and is characterized in that the gas generated by shaking a predetermined amount of waste liquid placed in a sampling container under predetermined conditions is introduced into a sealed container filled with air and having an effective volume larger than the amount of gas generated, and the air pushed out of the sealed container by the introduced gas is introduced into a measuring container held upside down in water while still filled with liquid, thereby determining the amount of gas generated from the waste liquid. [Effects of the Invention]

[0009] According to the present invention, it is possible to confirm in advance whether or not the waste liquid will generate an amount of gas that will cause problems such as deformation of the tank due to vibration during transportation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a flow diagram of a measuring device that can suitably carry out the method for measuring the amount of gas generated from waste liquid according to the present invention. [Figure 2] 2 is a cross-sectional view showing the state of the area around the measurement container before and after air collection in the measurement device of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the method for measuring the amount of gas generated according to the present invention will be described with reference to the drawings. The method for measuring the amount of gas generated according to the embodiment of the present invention is intended for a case in which a waste liquid containing an acidic solution such as nitric acid or aqua regia is placed in a container and transported by a transportation means such as a truck, and the amount of gas generated when a waste liquid sample sampled from the waste liquid to be measured is shaken under predetermined conditions is measured. This measurement method makes it possible to measure the amount of gas generated easily and at low cost by using a measurement device such as that shown in Figure 1.

[0012] That is, the measuring device of Figure 1 is mainly composed of a sampling container 1 into which a predetermined amount of waste liquid sample S sampled from the waste liquid to be measured is placed, a sealed intermediate container 4 into which gas generated from the waste liquid sample S is introduced by shaking the sampling container 1, a measuring container 7 which collects air that has been previously filled in the intermediate container 4 and is pushed out of the intermediate container 4 by the introduced gas using the water displacement method, and transfer pipes 3 and 6 which connect these containers.

[0013] By using the above-mentioned measuring device, the amount of gas generated from the waste liquid to be measured can be measured more accurately. That is, when a container containing the above-mentioned waste liquid is vibrated, gases generated from the waste liquid, for example, an acidic solution such as nitric acid or aqua regia, are mainly nitrosyl chloride, chlorine gas, NOx gas, etc., all of which have a specific gravity higher than that of air, and chlorine gas, etc., are easily soluble in water.

[0014] Specifically, in the method for measuring the amount of gas generated according to an embodiment of the present invention, a predetermined amount of waste liquid sample S is first placed in a sampling container 1, such as an Erlenmeyer flask, which is then sealed with a first rubber stopper 2 and shaken under predetermined shaking conditions. This actively generates gas dissolved in the waste liquid sample S. The shaking conditions described above are preferably sufficient, taking into account the conditions during transportation by a truck or other transportation means. For example, the Erlenmeyer flask is preferably shaken for approximately 5 to 10 minutes, with the upper end of the flask grasped and the lower end moved back and forth at a stroke width of approximately 30 to 50 mm, 20 to 200 times per minute. Alternatively, a shaker may be used to perform reciprocating or gyrating shaking under similar conditions.

[0015] The gas generated from the waste liquid sample S by the shaking is then introduced into the intermediate container 4 via the first transfer pipe 3, which is made of a silicone tube or the like. The opening of this intermediate container 4 is sealed with a second rubber stopper 5, and the interior is pre-filled with air. Because the gas generated from the waste liquid sample S has a higher specific gravity than air, the opening of the gas outlet end of the second transfer pipe 6, which exhausts the gas from the intermediate container 4, is inserted into the intermediate container 4 so that it is positioned higher than the opening of the gas inlet end of the first transfer pipe 3. This allows the air that was previously filled in the intermediate container 4 to be pushed out by the gas introduced into the intermediate container 4.

[0016] In addition, within the intermediate container 4, the effective volume V between the gas inlet end of the first transfer pipe 3 and the gas outlet end of the second transfer pipe 6 is ensured to be larger than the amount of gas generated from the waste liquid sample S. As a result, even if the gas generated from the waste liquid sample S contains a gas that is easily soluble in water, such as chlorine gas, the gas generated from the waste liquid sample S can be replaced with the same volume of air that is less soluble in water and transferred to the downstream measurement container 7, so that the amount of gas generated from the waste liquid sample S can be accurately measured.

[0017] Next, the air pushed out from the intermediate container 4 is introduced into a measuring container 7, which is, for example, a measuring cylinder, via a second transfer pipe 6 made of a silicone tube or the like. This measuring container 7 is held upside down in a water tank 8 that stores water W, with the interior almost filled with water W. As a result, the air pushed out from the intermediate container 4 is collected in the measuring container 7 by the water displacement method. Therefore, the amount of gas generated from the waste liquid sample S can be determined by measuring the amount of this collected air.

[0018] That is, as shown in Figure 2, which shows (a) before air is introduced into the measurement container 7 and (b) after air is introduced, the volume V1 of air collected in the measurement container 7 while the water previously filled therein is being expelled by the air pushed out of the intermediate container 4, and the volume V2 of air in the second transfer pipe 6 increased by the air pushed out of the intermediate container 4 are measured, and the amount of gas generated by shaking the waste liquid sample S can be measured by adding these up.

[0019] Strictly speaking, as shown in FIG. 2(b), if the liquid level in the measurement container 7 after collecting the air pushed out from the intermediate container 4 is higher by a height H1 than the liquid level of the water W in the water tank 8, the pressure P1 of the air collected in the measurement container 7 is multiplied by the vapor pressure P of the water W as shown in the following formula 1. w The pressure added with the liquid head of height H1 by water W is atmospheric pressure P o becomes equal to [Formula 1] P+Pw+ρgH1=P o

[0020] As can be seen from the above formula 1, the pressure P1 of the air that is pushed out from the intermediate container 4 and occupies the volume V1 collected in the measurement container 7 is equal to the atmospheric pressure P o Rather than "P w +ρgH1”, so the volume V1 at this pressure P1 is reduced to atmospheric pressure P o Actual volume V converted to 1-act is expressed as the following equation 2 according to Boyle's law. "Formula 2" V 1‐act =[(P o -P w -ρgH1) / P o ]·V1

[0021] As can be seen from the above equation 2, the atmospheric pressure P o The actual volume of gas generated from the waste liquid under the conditions V 1-actis smaller than the volume V1 that occupies the measurement container 7, the volume V1 value, which is a safe value, may be used as is to estimate the amount of gas generated from S. On the other hand, as shown in FIG. 2(b), if the position of the boundary between the air remaining in the second transfer pipe 6 and the water W is lower by a height H2 than the liquid level of the water W in the water tank 8, then, contrary to the above formula 1, the liquid head of the height H2 due to the water W can be calculated by subtracting the atmospheric pressure P from the liquid head of the water W as shown in the following formula 3. o The pressure applied to the second transfer pipe 6 is the air pressure P2 plus the vapor pressure P of the water W. w The pressure is the sum of the above. [Formula 3] P2+P w =P o +ρgH2

[0022] Therefore, the volume V2 of air that has increased in the second transfer pipe 6 is calculated by dividing the volume V2 by the atmospheric pressure P o Volume V when converted to 2-act According to Boyle's law, the actual volume of the gas is V 2-act In contrast, volume V2 cannot be said to be a safe value, but in the case of water, even a liquid head of 1 m in height is only about 0.1 atmospheres at most, and volume V2 is usually smaller than volume V1, so there is no particular problem even if the liquid head mentioned above is ignored. [Formula 4] V 2-act =[(P o -P w +ρgH2) / P o ]·V2

[0023] The amount of gas generated from the waste liquid determined by the above measurement method can be used to determine whether or not the waste liquid can be delivered to an industrial waste disposal company. As a criterion for this determination, for example, an allowable upper limit for the amount of gas generated from the waste liquid may be determined in advance based on past actual values, and delivery may be determined if the amount is below this allowable upper limit, or the determination may be made based on an estimated maximum pressure inside the tank that increases due to gas generated by vibrations when the tank containing the waste liquid is transported.

[0024] The estimated maximum pressure can be determined, for example, by the following method: In the method for measuring the amount of gas generated according to the embodiment of the present invention, when the amount of waste liquid sample S sampled from the waste liquid to be measured and placed in the sampling container 1 is a, the amount of gas generated due to vibration when the waste liquid is loaded into a tank with a capacity b up to 100c% (0≦c≦1) of the capacity b and transported can be estimated by the following formula 5. [Formula 5] Amount of gas generated = (V1 + V2)b·c / a

[0025] Since the volume of air present in the gas phase of the tank before transportation is b(1-c), the ratio d (gas pressure after pressure increase / gas pressure before pressure increase) of the absolute pressure in the gas phase of the tank before and after the pressure increase due to the gas generated by the vibrations described above can be calculated using the following formula 6. If the absolute pressure after pressure increase calculated using the following formula 6 exceeds the maximum allowable pressure of the tank, it is preferable not to hand it over to an industrial waste disposal company. [Formula 6] Ratio d=[b(1-c)+(V1+V2)b c / a] / [b(1-c)]

[0026] Before performing the measurement using the above method, the waste liquid sample to be measured may be analyzed to confirm whether water-soluble gas is released due to vibration. Alternatively, after performing the measurement using the above method, the water in the water tank 8 may be analyzed to confirm whether gas generated from the waste liquid sample is dissolved. If the above confirmation shows that water-soluble gas is generated from the waste liquid due to vibration, it is preferable to add the estimated amount of water-soluble gas to the amount of gas generated V1 + V2 determined by the above measurement method, or multiply it by a safety factor. Next, the method for measuring the amount of gas generated from waste liquid according to the present invention will be described more specifically with reference to examples. [Example]

[0027] The measuring device shown in Figure 1 was assembled using equipment that can be easily procured at the work site, and the amount of gas generated when a waste liquid sample sampled from the waste liquid was shaken was measured. Specifically, 100 mL of waste liquid sample S was gently placed in a 500 mL Erlenmeyer flask serving as a sampling container 1, and the flask was closed with a first rubber stopper 2. A first transfer tube 3 made of a silicone tube was inserted into a through-hole that had been drilled in advance in the first rubber stopper 2. The position of the gas outlet end of the first transfer tube 3 was adjusted so that it was located above the liquid surface of the waste liquid sample S.

[0028] The other end of the first transfer pipe 3, i.e., the gas introduction end, was inserted into a 250 mL gas washing bottle serving as an intermediate container 4, which had been filled with air and capped with a second rubber stopper 5, through one of two through holes previously drilled in the second rubber stopper 5. The gas discharge end of a second transfer pipe 6 made of a silicone tube was further inserted into the intermediate container 4 through the other through hole in the second rubber stopper 5.

[0029] The gas inlet end of the first transfer pipe 3 opens deep into the gas washing bottle near the bottom, and the gas outlet end of the second transfer pipe 6 opens above the gas washing bottle. This leaves a 50 mL space between these openings. With this configuration, as described below, a gas heavier than air generated from the waste liquid sample S by shaking the sampling container 1 is introduced into the intermediate container 4 and gradually accumulates upward from the bottom, while the air previously filled in the intermediate container 4 is pushed out by the introduced gas heavier than air and exhausted from above.

[0030] The other end of the second transfer pipe 6, the gas introduction end, was inserted into a 250 mL measuring cylinder serving as a measurement vessel 7. This measurement vessel 7 was held upside down in 2 L of water (W) stored in a 3 L beaker serving as a water tank 8, with the measurement vessel 7 nearly filled with water W except for a small space at the top. In this state, as shown in Figure 2(a), the position α of the liquid surface (water surface), which is the interface between the air remaining in the measurement vessel 7 and the water W, was recorded, and the position β of the liquid surface, which is the gas-liquid interface in the second transfer pipe 6, was also recorded.

[0031] Next, the sampling container 1 containing the waste liquid sample S was shaken for 10 minutes at a stroke width of approximately 50 mm, at approximately 100 reciprocations per minute, to foam the waste liquid sample S. The gas generated by foaming of the waste liquid sample S was exhausted from the sampling container 1 and introduced into the intermediate container 4 via the first transfer pipe 3. The introduced gas then pushed out the air that had previously filled the intermediate container 4, and air of the same volume as the gas generated from the waste liquid sample S was introduced into the measurement container 7 via the second transfer pipe 6.

[0032] After the shaking of the sampling container 1 was completed, it was confirmed that almost no air bubbles remained on or near the liquid surface of the waste liquid sample S. Then, the displacement of the liquid surface in the measuring container 7 from before the shaking was measured from the scale on the measuring cylinder to measure the volume V1. The displacement of the liquid surface in the second transfer tube 6 from before the shaking was also measured using a ruler. The volume V2 was calculated by multiplying the displacement measured with the ruler by the cross-sectional area of ​​the flow path of the second transfer tube 6. The sum of the volume V1 of air collected by the measuring container 7 and the volume V2 of air increased in the second transfer tube 6 was 5 mL or less. In other words, the amount of gas generated from 100 mL of waste liquid sample S due to shaking was 5 mL or less.

[0033] As mentioned above, if the amount of gas generated from 100 mL of waste liquid sample is less than 5 mL, and if the amount of waste liquid charged into the 1 cubic meter tank is 80% of the tank's capacity, then according to Equation 6 above, the ratio of the pressure increase before and after vibration, d, will be approximately 1.2 times or less. Therefore, if the internal tank pressure before vibration is atmospheric pressure (0.10 MPa), the internal tank pressure after gas generation from the waste liquid due to vibration can be estimated to be approximately 0.12 MPa, so problems such as tank damage due to expansion are unlikely to occur. Furthermore, since the actual vibrations applied to the 1 cubic meter tank during transportation are thought to be milder than the shaking conditions of sampling container 1 in the above measurement method, the amount of gas generated from the waste liquid in the 1 cubic meter tank is expected to be smaller.

[0034] Specifically, since it is thought that rippling occurs only in the liquid surface area about 1cm below the liquid surface during transportation, the amount of gas generated from the above-mentioned 100mL waste liquid sample of less than 5mL is equivalent to less than 500mL of gas being generated from this liquid surface area of ​​approximately 10,000mL, and is therefore thought to be a reasonable value. In fact, there were previously about one or two cases of damage to one cubic meter tanks per year due to expansion, etc., but by using the above-mentioned measurement method to shake a 100mL waste liquid sample and confirming that there are no bubbles on the liquid surface due to foaming, and then using the amount of gas generated as the criterion for handing over to an industrial waste disposal company as being less than 5mL, problems such as expansion and leakage have not occurred in the past year and a half. [Explanation of symbols]

[0035] 1. Sampling container 2. First rubber stopper 3 1st transfer pipe 4 Intermediary container 5. Second rubber stopper 6 Second transfer pipe 7 Measuring vessel 8. Aquarium S Waste liquid sample W water V effective volume

Claims

1. A method for measuring the amount of gas generated when waste liquid is vibrated, comprising: shaking a predetermined amount of waste liquid placed in a sampling container under predetermined conditions to generate gas; introducing the gas into a sealed container filled with air and having an effective volume larger than the amount of gas generated; and introducing the air pushed out of the sealed container by the introduced gas into a measuring container held upside down in water while still filled with liquid, thereby determining the amount of gas generated from the waste liquid.

2. 2. The method for measuring the amount of gas generated from the waste liquid according to claim 1, wherein the amount of gas generated from the waste liquid is calculated by adding together the volume of the pushed-out air collected in the measurement container and the volume increased by the pushed-out air in a pipe introducing the pushed-out air from the intermediate container to the measurement container.

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