Reduction in steam cost when boiler delivers at lower than rated press
Reduction in steam cost when boiler delivers at lower than rated press
(OP)
If I have a boiler rated to produce steam at 10 bar but I use it to produce steam at 8.5 bar is there a way to calculate my energy savings ?





RE: Reduction in steam cost when boiler delivers at lower than rated press
RE: Reduction in steam cost when boiler delivers at lower than rated press
Yes, it is possible to determine your energy savings, but you need a lot more info. I assume that you must not know what your fuel input is? If you assume that your Boiler Efficiency doesn't change (it shouldn't change more than a percent or two), then based on the boiler duty at 8.5 bars and 10 bars you can determine the reduction in fuel flow or energy input.
Hope this helps. Post more info if things are still unclear.
RE: Reduction in steam cost when boiler delivers at lower than rated press
If this boiler is for power generation, the overall thermal efficiency is typically referred to as the "heat rate" of the cycle; the amount of "heat" into the cycle per amount of electric power out of the cycle. Operating a steam turbine at lower-than-design inlet pressure is typically not going to improve the turbine efficiency (unless, perhaps this is a plant derate and you would otherwise be throttling at the turbine inlet), but you should review the particulars for your application.
For some sort of process application, the calculation is similar in concept: (energy in)/(product out).
This ultimately translates into $$$ in each case. My point is that there is more to your question than the operation of the boiler.
Best regards.
RE: Reduction in steam cost when boiler delivers at lower than rated press
The question of whether savings can be made by running at the lower pressure will depend on the load on the boiler. For instance, if a steam load near to 5 000 lb/h has to be sustained, then another boiler may have to be brought on line. This would offset any savings made by running at lower pressures. If, however, the maximum steam load can be guaranteed to be near 3 500 lb/h, the boiler will be able to cope and it is possible that fuel savings will occur. These savings are due to a higher heat transfer efficiency and lower radiation losses, but it should be stressed that such savings are likely to be marginal (probably less than 0.5%).