The whys of Combined Cycle power plants

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Discussion Overview

The discussion revolves around the feasibility and efficiency of using coal as fuel in combined cycle power plants, specifically examining the Brayton and Rankine cycles. Participants explore the technical challenges, operational considerations, and alternative methodologies for improving efficiency in coal power plants.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question why coal cannot be used in combined cycle power plants, suggesting that the turbine would be driven by hot exhaust gases rather than coal particles.
  • Others argue that using coal poses challenges due to the abrasive nature of unburnt coal ash, which could damage turbine blades.
  • It is noted that while some research has been conducted on coal-fired jet engines, practical issues such as coal dust behavior and turbine design have hindered commercial viability.
  • Participants discuss the efficiency of gas turbines compared to steam turbines, attributing higher efficiency to the ability of gas turbines to operate at higher temperatures.
  • Some contributions mention that the design of gas turbines is sensitive to impurities in the combustion gases, which are prevalent in coal combustion.
  • There are inquiries about methodologies for improving efficiency in coal power plants, particularly regarding the use of Rankine cycles.
  • Concerns are raised about the operational complexities and inefficiencies associated with coal supply chains compared to gas fuel systems.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using coal in combined cycle power plants, with no consensus reached on the viability or efficiency of such systems. The discussion remains unresolved regarding the methodologies for improving coal power plant efficiency.

Contextual Notes

Participants highlight limitations related to turbine design, operational challenges, and the impact of impurities in combustion gases, but these aspects remain unresolved within the discussion.

  • #31
hi every1 ,
I'm trying to do the concept of a turbosteamer that the bmw is workking on but I'm facing few problems :
the flow rate of water will be 9 ml/s and of pressure 6 bars . based on htri xchanger program , the best design of my shell and tube heat xchanger will be of 22 cm diameter and 6.4 mm tube diameter where number of tubes will be 215 and the length will be around 0.5 meters.

my problem is how to allow this very low flow rater ( 9 ml/s) enter the 215 tubes equally ?

my 2nd problems is that i have no experience with microturbines , i need to know how to design that turbine, ihope you can help guys

thank you
 
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  • #32
This thread on gas turbines has pretty well run its course. I suggest you open a new thread on steam turbines, & maybe one on heat exchanges. Both of your questions are interesting.
 
Last edited:
  • #33
hehe we can just open it here :)
 
  • #34
This thread gained life of its own!
 
  • #35
Pkruse said:
But DOD is demanding & getting much longer overhaul intervals.

They are slowly (but slowly) getting more rational about their specifications, as well.

Time was when the engine specification for a military aircraft said very little except "the engines will operate normally over the full performance envelope of the aircraft". If the engine designer phoned somebody in the air force to try to undertand this better (this was in the era before email), the standard answer was "but we won't know what the performance envelope will be until we have flown the prototype". Face-palm...
 

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