Generally speaking, neutral desiccant (food grade calcium chloride) can not dry alkaline gas, can dry acid gas and neutral gas; alkaline desiccant can not dry acid gas, can dry alkaline gas and neutral gas; The drying agent can dry various gases. However, this is only considered from the perspective of acid-base reaction. At the same time, some specialities other than regularity should be considered. For example, if a redox reaction occurs between a gas and a desiccant, or a complex, an adduct, etc. This desiccant cannot be used to dry the gas.

Food grade calcium chloride is selected as a neutral desiccant for example:

1 Do not use concentrated sulfuric acid to dry reducing gases such as H2S and Br2, because they will undergo redox reactions, such as H2S+H2SO4==2H2O+SO2+S↓

2 The H2S gas cannot be dried with anhydrous copper sulfate, and the two will react: CuSO4+H2S==H2SO4+CuS↓

3 can not dry NH3 with anhydrous copper sulfate, the two can react to form a complex: CuSO4 + 4NH3 = {Cu (NH3) 4} SO4

4 Can not dry NH3 with anhydrous CaCl2, the complex reaction will occur, and some adducts will be formed. CaCl2+4NH3=CaCl2•4NH3 CaCl2+8NH3=CaCl2•8NH3

In addition, for liquid desiccant, it is generally installed in a gas cylinder (gas is fed from a long tube, short tube), and the solid desiccant is contained in a drying tube or a U-tube.