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Commonly used static nitrogen distribution technology of liquid nitrogen

Time: 2017-07-07 10:09 Source: Bander liquid nitrogen tank Author: admin Click: second
Commonly used static nitrogen distribution technology of liquid nitrogen
Static nitrogen distribution of liquid nitrogen is to add a certain amount of liquid or feed gas into the container of known volume of dilution gas, and mix evenly. According to the amount of liquid or feed gas added and the volume of container, the concentration of liquid nitrogen can be calculated. The commonly used static nitrogen distribution technologies are as follows:

1、 Syringe nitrogen method

It is very convenient to use syringe for nitrogen distribution in the work with small gas demand. Take two syringes of different sizes. The large syringe is usually 100 ml, and the small syringe is determined according to the nitrogen distribution. During nitrogen distribution, put a small metal sheet in the large syringe, push the piston in, and then take a certain amount of feed gas from the small syringe. Connect the two syringes according to figure 2. Push the gas from the small syringe into the large syringe, remove the small syringe and rubber cap, pull the piston of the large syringe, dilute the gas to 100 ml with clean air, and shake the metal sheet in the syringe to make the gas mix evenly In other words, a lower concentration of liquid nitrogen is obtained. The concentration after dilution can be calculated according to the volume of gas before and after dilution. If the primary dilution can not meet the requirements, the second static nitrogen distribution technology of liquid nitrogen can be carried out. Although the technology has the advantages of simple equipment and easy operation, due to its small amount of nitrogen distribution, and the concentration of gas will change in the process of taking gas, the gas demand is larger or the ventilation time is shorter than [yds-47-127f] liquid nitrogen tank ]It is not suitable for long-term work, so it is necessary to use dynamic nitrogen distribution technology to prepare liquid nitrogen.

2、 Nitrogen distribution in large bottles

Clean and dry the large volume glass bottle or polyethylene plastic bottle, fill it with clean air instead of the original gas in the bottle, draw it into negative pressure, and then fill in a certain amount of liquid or raw gas. If the raw material is a gas at room temperature, add it with a gas quantitative tube (see Fig. 1) and fill it with clean air to atmospheric pressure. If the raw material is a volatile liquid, a certain amount of liquid can be weighed in a small Anpei bottle, put it into a large bottle, extract air to make it negative pressure, and then shake the ampoule. After the liquid volatilizes, fill clean air to atmospheric pressure.

The actual concentration of liquid nitrogen prepared in large bottles is often lower than the calculated value due to the adsorption of the wall. In order to avoid this effect, the first prepared gas can be removed after a period of time, and then the second nitrogen distribution can be carried out. This can reduce the adsorption of the bottle wall. If a lower concentration of gas is needed, after nitrogen is mixed in a large bottle, vacuum method can be used for dilution. For example, if the gas pressure in the large bottle is pumped to half of the original pressure, and then the clean air is filled to the original pressure, half of the original concentration of liquid nitrogen can be obtained.

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