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Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704 's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ordinary air.
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
Combustion of hydrogen with the oxygen in the air. When the bottom cap is removed, allowing air to enter at the bottom, the hydrogen in the container rises out of top and burns as it mixes with the air. Space Shuttle Main Engine burning hydrogen with oxygen, produces a nearly invisible flame at full thrust. Hydrogen gas is highly flammable:
Larger amounts are supplied in metal tanks similar to gas cylinders, designed so a needle can fit through the valve opening. A syringe, carefully dried and flushed of air with an inert gas, is used to extract the liquid from its container. When working with pyrophoric solids, researchers often employ a sealed glove box flushed with inert gas.
The combustion of hydrogen with oxygen produces water vapor as its only product: 2H 2 + O 2 → 2H 2 O. However, air is a mixture of gases, and the most abundant gas in air is nitrogen. Therefore, the combustion of hydrogen in air produces oxides of nitrogen, known as NO x. In this respect, the combustion process is much like other high ...
The autoignition temperature or self-ignition temperature, often called spontaneous ignition temperature or minimum ignition temperature (or shortly ignition temperature) and formerly also known as kindling point, of a substance is the lowest temperature at which it spontaneously ignites in a normal atmosphere without an external source of ignition, such as a flame or spark. [1]
Hydrogen gas released in this way can be used as hydrogen fuel, but must be kept apart from the oxygen as the mixture would be extremely explosive. Separately pressurised into convenient 'tanks' or 'gas bottles', hydrogen can be used for oxyhydrogen welding and other applications, as the hydrogen / oxygen flame can reach approximately 2,800°C.
Oxyhydrogen is a mixture of hydrogen (H 2) and oxygen (O 2) gases. This gaseous mixture is used for torches to process refractory materials and was the first [1] gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing ...