Most steam systems have nominal HP, MP and LP headers. Typically, HP steam is ~40bar, MP steam ~10bar and LP steam ~3bar. These pressures, chosen at the design stage, are not necessarily the most energy efficient. Rather than run at 'design' pressure, it is generally better to experiment by monitoring fuel consump tion as the HP/MP/LP pressure set points are slowly changed to find the optimum combination.
Turbines use less steam if inlet temperature is increased. This is especially important for condensing steam turbines (See Section 22.214.171.124). Thus, the HP system should run at maximum allowable temperature since the majority of HP users are steam turbines. Conversely, steam reboilers can be bottlenecked if the steam supply is superheated since in this case, the heat transfer coefficient is low until the temperature falls to the point where the steam-side of the reboiler tubes is wet. However, rather than lower the header temperature (if it also feeds steam turbines), it is better to install local de-superheaters for steam reboilers.
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