What does "three level safety education" mean

The liquefaction of gases can be divided into forward and reverse cycles. The forward cycle process is the absorption of heat from the higher temperature external heat source and the release of heat to the lower temperature external heat source. The reverse cycle is when the mass draws heat from a lower temperature external heat source and releases it to a higher temperature external heat source. The forward cycle converts heat energy into mechanical energy and the reverse cycle converts mechani...

Distillation is using the different boiling points of the two substances to condense the mixed steam and vaporize the mixed liquid repeatedly to achieve gas separation. For a mixed liquid composed of two substances with different boiling points, when the heat absorption part evaporates, the volatile components will evaporate more, while the mixed steam will give off heat and partially condense, the non volatile components will condense more. If the saturated steam with higher temperature is mixed with the saturated liquid with lower temperature, the steam will release heat and partially condense, and the liquid will absorb heat part of it evaporates. If after a round of partial evaporation and partial condensation, the steam and liquid with higher concentration will contact with the steam and liquid with different temperature respectively, and then partial condensation and partial evaporation will occur again. This process will be repeated for many times, and finally gas separation