What does “N” in 150 Nm3/h of nitrogen production mean?

Nm3 refers to a standard cubic volume, which is the volume of a gas under standard conditions. It is actually a unit of amount of substance that can be interchanged with mol; 1 mol of gas occupies a volume of 22.4 L under standard conditions.

Standard volume, the volume of a gas under standard conditions. . . .

N does not stand for Normal, but rather Nominal. Nm3 represents the volume at nominal conditions; these nominal conditions can be agreed upon by both parties. For example, they could be 1 atm and 0°C (i.e., standard conditions), or 100 kPa and 15°C. If no agreement is reached, in China the standard values are usually 1 atm and 20°C, while in international projects it is typically 100 kPa and 15°C. For instance: Nitrogen gas output: 150 Nm3/h (STD: 1 atm, 0°C), meaning that this Nm3 value refers to the volume of nitrogen gas at 1 standard atmosphere pressure and 0°C. Nitrogen gas output: 150 Nm3/h (100 kPa, 15°C), meaning that this Nm3 value refers to the volume of nitrogen gas at 100 kPa and 15°C. Nitrogen gas output: 150 Nm3/h (100 kPa, 20°C), meaning that this Nm3 value refers to the volume of nitrogen gas at 100 kPa and 20°C. These three values of Nm3 can be converted into one another, with minimal differences. In recent years, the internationally accepted standard state has seen 100 kPa replace 1 atm, while the temperature is a recommended value; in China, 20°C is commonly used, whereas internationally 15°C (60°F) is preferred. In fact, either value is acceptable as long as both parties agree on it. Even if no agreement is reached, it’s easy to reach an understanding, as the error margin is small. Moreover, the nominal operating conditions are often used in gas handling equipment such as compressors, blowers, and vacuum pumps, where it is customary to describe parameters based on the conditions of the gas entering the equipment. Normal and Nominal are quite similar, but they’re not the same thing, haha.