JPS6146199B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating water for testing liquefied petroleum gas containers, and more particularly to a method for deodorizing water. Liquefied petroleum gas (hereinafter referred to as LPG) is stored in high-pressure containers and supplied as fuel to households, factories, and automobiles. This high pressure container (hereinafter referred to as container)
has been used dozens of times between consumers and LPG filling stations.
Once every three or six years, they undergo a pressure test to ensure their safety before being reused. The liquefied petroleum gas inspection station (hereinafter referred to as the inspection station) collects containers that have exceeded their expiry date from the liquefied petroleum gas filling station (hereinafter referred to as the LPG filling station). Then, the remaining LPG is collected, the pressure is reduced and the vaporized material is removed, the valve is removed, the container is filled with water, water pressure is applied in the water tank, and the pressure resistance is determined based on the degree of expansion of the container. investigate. Those that pass the test are reused after draining the water inside them, drying them with warm air, removing rust, and painting them. LPG is odorless, and odorants are added to prevent accidents due to gas leaks.
In Japan, the "High Pressure Gas Control Law" and the "Liquefied Petroleum Gas Security and Proper Trade Law" stipulate that when 1/200th of LPG is present in the air, it can be detected by odor. are doing. The essential conditions for odorants include sensitivity, toxicity, corrosivity, diffusibility, dispersibility, and water insolubility.Sulfur compounds include mercaptans and thioethers, and oxygen compounds include aldehydes, ketones, and esters. has been done. These odorants are sourced from LPG importers,
It is added at the manufacturer and is partially pressurized in a general high-pressure container as a liquid. Since LPG is used by evaporation from a high-pressure container, high-boiling hydrocarbons and other organic compounds tend to remain in the container. Or, it becomes resinous and adheres to the inner wall of the container. At the inspection site, the odor from this odorant is released into the workplace during the process of removing the valve, filling it with water, and draining the water inside. The process with the highest odor concentration is internal hot air drying, but all of this exhaust gas is led directly to the combustion furnace for deodorization. On the other hand, the amount of water used for testing varies depending on the type of container, approximately 120 for a 50 kg container and approximately 48 for a 20 kg container.
, approximately 24 for a 10Kg container, and a laboratory that tests 1000 bottles a day uses approximately 4 to 7 m ³ /hr. High boiling point oily substances, odorants, rust, etc. that adhere to the inner wall of the container due to the pressurization during the pressure test dissolve or flow out as an emulsion during the water removal process. This waste water is used to remove rust etc. in a sedimentation tank, then to an oil layer separation tank, where it is recycled and used again as test water. In order to stabilize the emulsion and prevent slime formation, make-up water is added to the water. Part of it has been released. Conventionally, some of this odorous discharged water was kept in a storage tank and mixed with oxidizing agents, surfactants, masking agents, etc. in batches before being discharged. However, these chemical treatments added for deodorization or odor control,
This was done empirically by laboratory workers who were accustomed to the smell of odorants, so there were many incomplete treatments.
This causes odors to emanate from the wastewater downstream.
Not only did it cause foul odor pollution, but it also gave the general population a sense of unnecessary danger. Here, the sensitivity of odorants is specified as one that causes psychological anxiety and danger, is easily distinguishable from commonly existing odors, is stable, and can be detected even at low concentrations. However, if the general population becomes chronically exposed to this odor, the purpose of LPG as an odor will disappear, and it will lead to explosions due to gas leaks. In addition, in order to reduce the odor in the vicinity of the inspection station, air was blown in after the oil layer was separated to remove the odor, but this was not found to be sufficiently effective. Based on such knowledge, the present invention aims to provide a method for treating test water of LPG containers with ozone, and in particular, a method for deodorizing the same. As is well known, ozone can be easily generated from air or oxygen by electrical discharge, and its strong oxidizing power is widely used in water purification, wastewater treatment, and odor removal. It is applied to deodorize treatment plants. Here, the reactivity of malodorous substances and ozone in the gas phase slows down in the order of amines, sulfur compounds, and hydrocarbons, and even hydrogen sulfide, which is a typical malodorous substance, is hardly oxidized when mixed with ozone for just a few minutes. No reaction takes place. However, the reaction in an aqueous solution system is rapid, and oxidation progresses to sulfate ions. Regarding deodorization of test water, as mentioned above, the method of expelling odors into the gas phase by air aeration does not work unless the odorant is incorporated into an emulsion dispersed in water and complete oil-water separation has been performed. It is not easily released into the phase. Therefore, a large amount of air is required, and the size of the exhaust deodorizing device is also increased. On the other hand, if the ozone deodorizing method according to the present invention is applied, the amount of gas sent into the waste water is small, ozone oxidation takes place in the waste water, and the odor of the odorant completely disappears. That is, due to the reactivity of ozone, deodorization can be performed without being hindered by the emulsion contained in the waste water. In addition, as mentioned above, in order to deodorize with ozone,
Of course, the water sent to the ozone reaction tower must be pretreated to remove precipitates and oily substances. That is, when fine particles such as rust are fed into the ozone reaction tower, they not only settle at the bottom of the reaction tower, but also clog the diffuser pipe through which ozone is injected, reducing the ozone contact efficiency. In addition, if a large amount of oily substances flow in, they will not be discharged from the lower part of the reaction tower and will remain in the upper part of the reaction tower for a long period of time.The oily substances will be oxidized by ozone, and will gradually turn into tar-like substances, causing the inner surface of the reaction tower. Attach to. In order to prevent such problems, the above-mentioned pretreatment is necessary. Here, the above-mentioned ozone is an air raw material and usually has a concentration of about 1 wt%, and the method uses the reaction tower and injects the ozone into the waste water introduced therein as fine bubbles to diffuse the ozone into the waste water. However, if there is nothing in the wastewater that reacts with ozone, it will be released into the exhaust gas as unreacted ozone. Since this ozone causes air pollution as an oxidant component if released without treatment, it is necessary to treat unreacted ozone in some way. The present invention also relates to the treatment of this unreacted ozone. Here, unreacted ozone can be decomposed by activated carbon, catalyst decomposition, thermal decomposition, and chemical cleaning methods, and activated carbon and catalysts, which require little operational control, are generally used. However, test water contains a large amount of volatile organic compounds, and the effective surface area of activated carbon and catalyst methods is significantly reduced. Pyrolysis method is 400
Ozone decomposes in less than 1 second at ℃. In the present invention, this characteristic is utilized to introduce the exhaust gas that has been brought into contact with the waste water into the combustion deodorizing furnace after internal hot air drying in the container inspection process. In this way, unreacted ozone contained in the exhaust gas is decomposed and volatile organic compounds are burned simultaneously, without causing air pollution. Furthermore, since the amount of gas used in the ozone oxidation method is much smaller than in the conventional air aeration method, it does not exceed the load on the combustion deodorizing furnace. In addition, if the wastewater from the reaction tower contains a large amount of substances that react with ozone, the wastewater will contain a large amount of odorants, similar to air aeration, so if it is led to a combustion deodorizing furnace, , this odor can also be reliably removed. Furthermore, conventional equipment can be used as is for the combustion deodorizing furnace, making it economical. In addition, ozone generators use a relatively large amount of cooling water in order to suppress the heat generated by the discharge phenomenon, and if this is used instead of the water that was conventionally supplied separately, the amount of water used can be increased. It is more economical. Therefore, the present invention also considers the use of this ozone generator cooling water as test water. Examples of the present invention will be described below. Ozonation of test water was carried out in countercurrent flow using a reaction vessel with an inner diameter of 10 cm and a height of 60 cm, which had a porous diffuser plate at the bottom. The wastewater to be treated is added at a constant flow rate from the top, and ozonized air with an ozone concentration of 1wt% is added once.
Inject using the air diffuser plate at a flow rate of /min.
The amount of ozone consumed was determined from the difference between the ozone concentration on the inlet side and the ozone concentration on the outlet side. After the ozone treatment, approximately 150 ml of the wastewater to be treated (hereinafter referred to as treated water) was placed in a 250 ml Erlenmeyer flask with a stopper, and an odor test was conducted. Odor was determined by a panel of 6 men and 3 women who conducted a sensory test of the treated water arranged in random order to judge the strength of the odor and obtained the results shown in Table 1.

[Table] The odor of LPG odorant is completely eliminated by treatment with ozone consumption of approximately 7.5 ppm, and a faint alcohol and aldehyde odor can be felt. Figure 1 shows the results of gas chromatogram analysis using benzene extraction for raw water, ozonated water (ozone consumption: 15 ppm), and tap water. 2 ml of special grade benzene was added to 100 ml of each sample water, and after extraction using a separator, the benzene solution was measured using a gas chromatogram analyzer equipped with an FPD. In the figure, A is tap water, B is raw water for inspection wastewater, and C is ozone-treated water. These sample water A,
Impurities in benzene were found in both B and C, and dimethyl disulfide and diisopropyl sulfide were found in raw water B, which was the wastewater for testing. Ozone treatment completely eliminates these sulfur compounds as odorants. A second embodiment of an inspection water system employing the present invention is shown below.
As shown in the figure. In the figure, 1 is the same inspection work building as before, 2 is a sedimentation tank for testing water, 3 is an oil-water separation tank,
4 is a reuse test water tank, 5 is an ozonated raw water tank,
6 is an ozone reaction tower, and 7 is an ozone generator. The wastewater generated in the process of draining water from the LPG container described above passes through a settling tank 2, an oil-water separation tank 3, and a reuse test water tank 4, and is circulated and reused by a pump 8. Cooling water discharged from the ozone generator 7 is continuously used as make-up water in the inspection process. Water that exceeds the amount held in the sedimentation tank 2, oil-water separation tank 3, and reuse inspection water tank 4 enters the ozone treatment raw water tank 5.
The amount of water is detected by the level meter 9, the pump 10 and the ozone generator 7 are operated intermittently, the water is deodorized by ozone in the ozone reaction tower 6, and then discharged. Since testing water does not require high-quality water, in this method, if the water is clean during the work process, the ozone generator 7 is stopped and the supply of make-up water is stopped, and the water is recycled as usual until the water deteriorates. You can also do it. The ozone-treated exhaust gas generated from the ozone reaction tower 6 is sent through an exhaust pipe 11 to a direct combustion furnace 12, which is an exhaust deodorizing device for drying hot air inside the container, and is rendered harmless. That is, since the exhaust gas from the ozone reaction tower 6 contains unreacted ozone and volatile organic compounds such as odorants, the direct combustion furnace 12 decomposes the unreacted ozone and decomposes the volatile organic compounds. Burn it to make it harmless. Next, another embodiment is shown in FIG. 3, in which the same parts as in FIG. 2 are given the same reference numerals. In this testing water system, the entire amount of testing water is treated with ozone to reduce odors in the workplace. The difference from the embodiment shown in FIG. 2 is that the reuse test water tank 4 is placed after the ozone reaction tower 6. In this case, pump 8 needs to have a larger capacity than pump 10, other things being the same. This method uses 5m ³ /hr of water.
If the ozone injection amount is 10ppm, the output will be 50g/hr.
ozone generator is required, and the amount of cooling water is 0.36m ³ /h.
7.2% of make-up water is added per hour, and work can be done with a constant water quality without material corrosion due to a drop in the pH of the water due to ozone treatment. As described above, according to the present invention, the test water discharged from the liquefied petroleum gas container is brought into contact with the ozone gas generated by the ozone generator, so that the bad odor generated from the test water can be effectively deodorized. Furthermore, since the conventional direct combustion furnace can be used to treat exhaust gas containing unreacted ozone and volatile organic compounds after ozone treatment, it is an economical method of odor prevention that does not require new special equipment. be.

[Brief explanation of the drawing]

Fig. 1 is a gas chromatogram showing the results of the present invention in comparison with tap water and untreated water, and Fig. 2 is an example of the equipment configuration for carrying out the method of treating liquefied petroleum gas container inspection water according to the present invention. System explanatory diagram, FIG. 3 is a system explanatory diagram showing another configuration example for implementing the present invention. 1... Inspection work building, 2... Sedimentation tank, 3...
Oil/water separation tank, 4... water tank for reuse inspection, 5... ozone treatment raw water tank, 6... ozone reaction tower, 7... ozone generator, 12... combustion furnace.

Claims (1)

[Scope of Claims] 1 Test water discharged from a liquefied petroleum gas container is treated to remove rust and surface oil layers to the extent that it contains emulsion, and then brought into contact with ozone gas produced by an ozone generator. , a method for treating water for testing liquefied petroleum gas containers, characterized by performing deodorization treatment. 2. After the test water discharged from the liquefied petroleum gas container is treated to remove rust and surface oil layers to the extent that it contains emulsion, it is brought into contact with ozone gas produced by an ozone generator to deodorize it, and After contacting this test water, the exhaust gas containing unreacted ozone and volatile organic compounds is led to a combustion furnace.
A method for treating water for inspection of liquefied petroleum gas containers, characterized by thermally decomposing unreacted ozone and burning volatile organic compounds.