Chapter 10- PROPULSION BOILERS 



TO 

 STACK 



FEED WATER 



ECONOMIZER 



ADDITIONAL 



SOURCE OF 



POWER FOR 



AIR COMPRESSOR 



FEED WATER 



COMBUSTION AIR 



-TURBINE 



COMPRESSOR 



COMBUSTION GASES 



TO 



DE5UPERHEATER 

 IN BOILER DRUM 



SUPERHEATED STEAM TO ENGINES 



BURNERS 



PRESSURE-TIGHT 

 BOILER FURNACE 



GENERATING 

 ELEMENTS 



SUPERHEATER 

 ELEMENTS 



147.86 



Figure 10-25.— Schematic view of pressurized-furnace boiler. 



kind of energy transformation that occurs in a 

 steam turbine; the difference is that hot com- 

 bustion gases, rather than steam, carry the 

 energy to the gas turbine. After the combustion 

 gases leave the gas turbine, some of the remain- 

 ing heat may be used to heat feed ^water as it 

 flows through an economizer. 



There are no forced draft blowers in pres- 

 surized-furnace boiler installations. The super- 

 charger takes the place of the forced draft 

 blowers, thus greatly increasing plant efficiency. 

 The steam saved by the use of a supercharger 

 instead of forced draft blowers may amount to as 

 much as 8 or 10 percent of boiler capacity. 



Altogether, a pressurized-furnace boiler is 

 not much more than half the size and half the 

 weight of a conventional boiler of equal steam 



capacity. A large part of this saving of space and 

 weight occurs because the increased pressure^ 

 on the combustion gas side causes a very great 

 increase in the rate of heat transfer to the water 

 in the tubes. Thus a smaller generating surface 

 is required to generate the same amount of 

 steam. Another cause of space and weight saving 

 is that the general design of the pressurized- 

 furnace boiler eliminates the need for much of 

 the refractory material that is required in other 



Forced draft blowers for conventional boiler instal- 

 lations furnish air pressures ranging from to 10 

 pslg. In a pressurized-furnace boiler, the air com- 

 pressor supplies combustion air at pressures ranging 

 from 30 to 90 psig. 



259 



