Carbon dioxide cylinder

The poster has engaged in two dangerous and illegal practices. According to the requirements of the TSGR0006-2014 Regulations on the Safety Supervision of Gas Cylinders: 1. Gas cylinders must not be used interchangeably; the poster used a carbon dioxide cylinder to store nitrous oxide, which is an illegal practice. 2. Gas cylinders must not be heated in any way

The original poster probably made a typing mistake, but heating gas cylinders is really excessive~ Does the original poster have some particular idea in mind?

Heating the gas cylinder in a water bath is against the operating procedures, right?

:I’m sorry; carbon dioxide cylinders are used to store carbon dioxide. There was a mistake in the entry – it was typed as nitrogen dioxide. Sorry!

@Special question: Which specification states that it is prohibited to use any heat source to heat gas cylinders? Could you please explain in detail the full name of this standard? Thank you!

TSGR0006-2014 Regulations on Safety Inspection of Gas Cylinders

@Special: I went to look for it specifically just now, and there indeed is such an exact quote. Thank you!

Carbon dioxide cylinders are high-pressure containers with a critical temperature of 31.1°C; above this critical temperature, the gas cannot be liquefied. If the temperature of a liquid carbon dioxide cylinder exceeds 31.1°C, carbon dioxide will remain in gaseous state regardless of the pressure, failing to liquefy; as a result, the pressure inside the cylinder will rise sharply, posing a risk of explosion. Therefore, when storing, transporting, and using carbon dioxide cylinders, cylinders rated at 150 kg/cm2 or 200 kg/cm2 must be used, and they can only be put into use after passing strict inspections. It is necessary to strictly comply with the relevant provisions in the \"Cylinder Safety Supervision Regulations\" issued by the former Ministry of Labor; during storage and transportation, exposure to sunlight must be strictly avoided, and hitting, collision, or heating are strictly prohibited, as well as keeping the cylinders away from heat sources. When carbon dioxide is depressurized through a gas cylinder, it absorbs a large amount of heat, causing the cylinder to frost over and even potentially freezing the valve stem. When the carbonation valve freezes, it must not be struck or heated with fire; instead, it should be rinsed with tap water to warm it up. The nominal working pressure of carbon dioxide cylinders is 15 MPa, and the pressure after filling is only 7–8 MPa, which is far below the nominal working pressure. Why then is it emphasized that overfilling is strictly prohibited, and must filling be carried out according to a standard of 0.6 kg/L? Answer: It is a high-pressure liquefied gas among bottled gases, with a critical temperature of 31°C. When the temperature is below 31°C, it can be liquefied by applying pressure; when the temperature is equal to or above 31°C, the liquid carbon dioxide in the bottle turns into gaseous carbon dioxide. When carbon dioxide is filled at a standard rate of 0.6 kg/L, at a temperature of around 31°C, the pressure inside the bottle corresponds to a gas-liquid coexistence state, with the saturated vapor pressure at the liquid interface being 7.39 MPa. When the temperature reaches or exceeds 31°C, a phase change from liquid to gas occurs; the pressure inside the bottle is no longer determined by the saturated vapor pressure of carbon dioxide, but rather by the sudden increase in pressure resulting from the massive vaporization of liquid carbon dioxide. At this point, the pressure condition inside the bottle is essentially the same as that of a perfect gas. As the temperature continues to rise to 54°C, the pressure inside the bottle increases to about 15 MPa, which is equivalent to the nominal operating pressure of the gas cylinder. Due to these characteristics of bottled carbon dioxide, in order to ensure the safety of gas cylinders during filling, storage, transportation, and use, they must be filled strictly in accordance with the specified filling systems. A gas cylinder is a separate, thin-walled, insulated container; the pressure of carbon dioxide inside it depends not only on temperature but also on the amount of gas filled in it. The nominal working pressure of a gas cylinder refers, for cylinders containing permanent gases, to the specified filling pressure of the gas at 20°C; the amount of gas filled is measured in terms of pressure ； For cylinders containing high-pressure liquefied gases such as carbon dioxide, the specified value refers to the gas pressure inside the cylinder at a temperature of 60°C, and the filling volume is measured in terms of weight. If the filling is not done at a rate of 0.6 kg/L but instead involves overfilling, the gas space inside the bottle decreases accordingly. As the temperature rises, the volume of liquid carbon dioxide expands, further reducing the gas space, until eventually the bottle becomes completely filled with liquid and no gas space remains. Table 2: Full-liquid temperature at different filling coefficients. Filling coefficient/kg•L-1: 0.790, 0.750, 0.688, 0.664; Full-liquid temperature (°C): 18.1, 21.8, 26.3, 28.4. When the bottle is filled to capacity, the pressure is no longer the saturated vapor pressure; instead, it is caused by the expansion force of liquid carbon dioxide. This expansion force is much greater than the saturated vapor pressure. The volume expansion system for liquid carbon dioxide is relatively large; within the range of -5 to 35°C, for every 1°C increase in temperature, the pressure inside the cylinder increases by 0.314–0.0834 MPa. Therefore, rapid filling can easily lead to overpressure and explosion of the gas cylinder.