2 replies to this topic

[Rahimzadeh]

Dears:

I want to know how i can change a saturated steam at 9 barg to superheated steam at 7 barg pressure with 172 centigrade with manual valve?

Best for you]

M.R.Rahimzadeh

[mayurhardrock3]

Sorry there is no way to do it.....

[katmar]

Theoretically it is possible, but it is unlikely to happen in a normal chemical plant.

If you are at a location where your atmospheric pressure is 101 kPa abs then saturated steam at 9 bar g would have an enthalpy of 2775 kJ/kg. If you look up in the steam tables for superheated steam at 7 bar g to see what temperature you require to match this enthalpy you will find that 173 °C matches. So if your 9 bar g steam was perfectly dry and your system was well insulated you could drop the pressure through a valve and get slightly superheated steam.

The problem is in getting perfectly dry 9 bar g saturated steam. If this steam contained 2% of moisture (which would be quite good quality steam in most plants) then the enthalpy is only 2735 kJ/kg (weighted average for vapor and liquid) and when you drop the pressure to 7 bar g the steam will be saturated and still contain about 1,5% liquid.