Can Dewar flasks be used to store carbon dioxide? Applicable conditions and safety regulations

In fields such as industrial welding, food cold chain, and scientific research, the demand for cryogenic storage and transportation of carbon dioxide is increasing. Many practitioners wonder, "Can Dewar flasks be used to store carbon dioxide?" The answer is: Dewar flasks that meet specific conditions can be safely filled with carbon dioxide, but ordinary Dewar flasks must not be used indiscriminately. This article will analyze in detail the compatibility principles, applicable conditions, safety regulations, advantages of high-quality equipment, and application scenarios for storing carbon dioxide in Dewar flasks, providing professional reference for related selection and use.

The core design logic of Dewar flasks for storing carbon dioxide is based on the principle of cryogenic insulated storage and transportation. Carbon dioxide has a critical temperature of 31.1℃ and a critical pressure of 7.38MPa. It cannot be liquefied under pressure at room temperature and must be converted into solid dry ice or liquid in a cryogenic environment (below -78.5℃). Dewar flasks employ a high-vacuum, multi-layered insulated structure, effectively blocking heat conduction and maintaining an internal cryogenic environment below -78.5℃. This allows carbon dioxide to be stored stably in either liquid or solid form. Simultaneously, precise pressure control prevents sudden pressure increases due to phase changes, ensuring safe storage and transportation. Ordinary Dewar flasks (such as conventional liquid nitrogen and liquid oxygen Dewar flasks) are not optimized for the phase change characteristics of carbon dioxide and are prone to pressure runaway risks; therefore, they are not universally applicable.

Using Dewar flasks for storing carbon dioxide requires meeting three core applicable conditions. First, equipment selection and compatibility: Dewar flasks specifically labeled "suitable for carbon dioxide" must be used. These flasks have inner liners made of low-temperature resistant stainless steel to withstand the corrosive effects of carbon dioxide at low temperatures, and are equipped with suitable pressure regulators (pressure control range 0.6-1.6 MPa) to meet the phase change pressure requirements of carbon dioxide. Second, filling standards must be met: Filling must be performed by a qualified and reputable company. Before filling, the pipeline must be purged with dry nitrogen to remove impurities and moisture. The filling volume must be strictly controlled within 85% of the total volume, leaving sufficient space for phase change expansion; overfilling is strictly prohibited. Third, environmental and operational condition compatibility: The storage environment must be well-ventilated, away from fire sources and high-temperature equipment, and the ambient temperature must not exceed 30℃. Shock-absorbing devices must be provided during transportation to prevent damage to the insulation layer from violent collisions.

Safety compliance is the core guarantee for Dewar flask-packaged carbon dioxide, and four key points need to be emphasized. 1. Equipment Inspection: Before use, carefully inspect the Dewar flask for any dents or corrosion. Confirm that valves, pressure gauges, safety valves, rupture discs, and other safety devices are intact and leak-free. Check the vacuum insulation performance; if abnormal frost appears on the outer casing, stop using it immediately.

2. Operational Protection: Operators must wear cryogenic gloves, goggles, and cold-weather clothing to avoid direct contact with cryogenic pipelines or leaking carbon dioxide to prevent frostbite. Smoking and open flames are strictly prohibited in the operating area; dry powder fire extinguishers and other fire-fighting equipment must be available.

3. Leakage Handling: In case of a minor leak, immediately evacuate personnel, increase ventilation, and close relevant valves. In case of a large leak, demarcate a warning area and contact professional personnel for handling. Do not disassemble the equipment yourself.

4. Regular Maintenance: Regularly perform vacuum testing, valve calibration, and pipeline replacement on the Dewar flask. Unauthorized modification or disassembly of safety devices is strictly prohibited. Maintain complete maintenance records.

High-quality carbon dioxide-specific Dewar flasks possess three core advantages. Firstly, it boasts high-efficiency insulation: employing a high-vacuum multi-layer insulation process and high-quality insulation materials, it features a low static evaporation rate of liquid carbon dioxide, resulting in a long storage time and reduced operating costs. Secondly, it is safe and reliable: equipped with fully imported valves, high-precision pressure gauges, and overpressure relief devices, ensuring precise pressure control and comprehensively mitigating the risk of pressure runaway. Thirdly, it is durable and adaptable: the inner liner is made of corrosion-resistant stainless steel, offering strong impact resistance and adaptability to frequent transportation and long-term storage needs, with a service life of 8-10 years. Some high-end models support remote liquid level and pressure monitoring, suitable for intelligent operation and maintenance scenarios.

Its applications are wide-ranging. In the industrial field, it can be used for carbon dioxide shielded welding and the storage and transportation of chemical reaction raw materials; in the food industry, it is suitable for dry ice refrigeration in cold chain transportation and the storage of raw materials for carbonated beverage production; in the scientific research field, it can be used as a refrigerant or reaction medium for low-temperature experiments; in addition, it is also used in fire fighting, medical emergency, and other scenarios. When selecting a model, it is necessary to match the Dewar flask capacity (50L-500L optional) and pressure specifications according to specific working conditions, and prioritize manufacturers with pressure vessel production qualifications and providing comprehensive after-sales maintenance services.

In summary, specialized Dewar flasks can be safely filled with carbon dioxide, but strict adherence to equipment compatibility, filling specifications, and safe operating procedures is required. Ordinary Dewar flasks, due to their structural and performance limitations, cannot be filled arbitrarily. Selecting high-quality specialized equipment and using it correctly can fully leverage the advantages of low-temperature storage and transportation using Dewar flasks, ensuring the safe and efficient storage and transportation of carbon dioxide.