True 8lended Heav. .esiduals .
General Fuel Type Distillate & Distillates & High-As.
Naphthas Low-Ash Crudes Crude
Fuel pre-heat No Yes Yes
Fuel atomization Mech/LP air HP/LP air HP air
Desalting No Some Yes
Fuel inhibitation Usually none Limited Always
Turbine washing No Yes， except distillate Yes
Start-up fuel With naphtha Some fuels Always
Base fuel cost Highest Intermediate Lowest
Description High-quality distillate Low-ash， limited contaminant Low-volatility
essentially ash-free levels High-ash
Types of fuels included True distillates (naphtha， High-qualitycrudes， slightly Residuals and low-grade
kerosene， no. 2 diesel， no. 2 fuel contaminated distillates crude (No. . fuel，
oil，IP-4， IP-5) Navy distillate No. . fuel， Bunker C.
ASTM designation 1-GT，2-GT， 3-GT 3-GT 4-GT
Turbine inlet temperature Highest Intermediate Lowest
.ue.. 43.
are most often present in the form of salt water， which results from saltywells， transport over seawater， or mist ingestion in an ocean environment. Fuel treatments are costly and do not remove all traces of these metals. Aslong as the fuel oil properties fall within specific limits， no special treatment is required. Blends are residuals that have been mixed with lighter distillates to improve properties. The specific gravity and viscosity can be reduced by blending. About 1% of total installed machines can operate on blends.
A final fuels group contains high-ash crudes and residuals. These account for 5% of installed units. Residual fuel is the high-ash by-product of dis-tillation. Low cost makes them attractive; however， special equipment must always be added to a fuel system before they can be utilized. Crude isattractive as afuel， since in pumping applications it is burned straight from the pipeline. Table 12-2 shows data obtained from a number of users that
Table 12-2
Operation and Maintenance Life of an Industrial Turbine
Firin. Temperature below Firin. Temperature above 1700 0F (927 0C) 1700 0F (927 0C)
Type of Application and Fuel Comb. 1st Stage 1st Stage Comb. 1st Stage 1st Stage Liners Nozzle 8lades Liners Nozzle 8lades
BASE LOAD Starts/hr十十十 Nat. gas 1/100030，00060，000100，00015，00025，00035，000 Nat. gas 1/107，50042，00072，0003，75020，00025，000 Distillate oil 1/100022，00045，00072，00011，25022，00030，000 Distillate oil 1/106，00035，00048，0003，00013，50018，000 Residual 1/10003，50020，00028，0002，50010，00015，000
Residual 1/10 SYSTEM PEAKING Normal Max. Load of short duration and daily starts Nat. gas 1/107，50034，00060，0005，00015，00024，000 Nat. gas 1/53，80028，00040，0003，00012，50018，000
Distillate 1/106，00027，20053，5004，00012，50019，000 Distillate 1/53，00022，40032，0002，50010，00016，000 TURBINE PEAKING
Operating Above 50 0F-100 0F (28-56 0C) Firing Temperature Nat. gas 1/52，00012，00020，0002，00012，50018，000 Nat. gas 1/1 4009，00015，000 40010，00015，000 Distillate 1/51，60010，00016，0001，70011，00015，000 Distillate 1/1 4007，30012，000 4008，50012，000
indicates a considerable reduction in downtime， depending on the type of service and fuel used. This table also shows that natural gas is by far the best fuel. The effect of various fuels on the output work of the turbine can be seen in Figure 12-1. This figure shows that vaporized fuel oil gives a higheroutput. This high output results when steam is mixed with the hot fuelgas， which enters the combustor at (371 0C). Corrosion effects have not beendetected with thisfuel， since the steam is not allowed to condense in the turbine.
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