Pure steam validation

Steam sterilization is the method mostly used to sterilize freeze-dryers. High-quality, ultra-pure steam (water for injection standard USP XXII or PhEur equivalent) is used to achieve a minimum exposure of 121 °C for 30 min or the equivalent temperature-time combination for effective sterilization (Table 2.4.1). This method is easy to validate and is recommended by regulatory authorities as being reliable. The definition of sterilization is a validated process used to render a product surface free of all forms of viable micro-organisms (EN 556-1 2001). According to the authorities, a product or surface is only sterile when a validated sterilization process has been applied (EN 550, EN 552, EN 554, EN ISO 14160 and EN ISO 14937). 

Fig. 4.3-7 Heat transfer at the condensation of pure steam. The lower straight line is valid for static steam...

D14. A distillation column with open steam heating is separating a feed that is 80.0 mol% methanol and 20.0 mol% water in a steady state operation. The column has 10 stages, a total condenser, and the feed is on stage 5. Operation is at 1.0 atm. The steam is pure water and is a saturated vapor. CMO can be assumed to be valid. At 2 16 a.m. 25 days ago the feed and distillate flows were shut off (D = F = 0), but the steam rate was unchanged and the total condenser is still condensing the vapor to a saturated liquid. The column has now reached a new steady state operation. 

Now we have listed all the important basic chemical properties of water molecules. Water as we know is a snbstance and is liquid at ambient temperatures. It turns into solid (ice) at lower temperatures below 0°C, or it boils at 100°C and changes into gas (vapor, steam in this case) under the standard condition. The standard condition here means that the atmospheric pressure is 1.0 atm (or 1.013 hPa or bar). Actually, the freezing point (temperature) and the boiling point of pure water under this condition are defined to be 0°C and 100°C, respectively. [Today, scientists try to redefine the standard condition to be 1.000 hPa or 1.000 bar (1,000 mbar) instead of 1 atm. For nonrigorons treatments, the old standard condition is still valid and is what is employed in this book]. 

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