Info

(Btu/lbm)

(Btu/hp-h)

(Btu/hp-h)

(Btu/hp-h)

(Btu/hp-h)

150 psig/D&S

1,196

11,264

15,018

17,298

20,517

250 psig/450°F

1,231

10,097

13,462

15,534

18,358

400 psig/550°F

1,276

9,487

12,649

14,661

17,248

600 psig/750°F

1,379

8,588

11,399

13,272

15,614

900 psig/900°F

1,459

8,123

10,775

12,433

14,754

purity and protection from erosion due to moisture and impurity deposits. Typical life-cycle O&M costs range from $0.002 to $0.006/hp-h ($0.003 to $0.008/kWh).

With steam turbines, system thermal efficiency varies far more than with reciprocating and gas turbine engines and is mostly a function of turbine design and steam supply and exhaust conditions (that is, the enthalpy, or heat, drop through the turbine}. Turbine mechanical efficiency typically ranges from 30 to 60% for single-stage turbines and from 50 to 80% for multi-stage turbines. System simple-cycle thermal efficiency typically ranges from 20 to 30% for condensing systems and from 5 to 15% for non-condensing systems. Assuming total steam flow and heat drop are fixed by given conditions, turbine mechanical efficiency selection should be based on the incremental capital cost for the more efficient turbine and the incremental value of increased power output.

A multi-stage condensing turbine can generate shaft power at a typical steam rate of 7 to 13 lbm/hp-h (4 to 8

kg/kWh). Accounting for boiler efficiency losses, this equates to heat rates ranging from 12,000 to 15,000 Btu/hp-h (15,000 to 21,000 kJ/kWh) on an HHV basis.

Fig. 29-17 Multi-Stage Steam Turbines Applied at Sugar Mill for Cane Knife and Mill Drives. Source: Tuthill Corp. Murray Turbomachinery Div.

Table 29-4 Representative Condensing Turbine Heat Rates Under Various Steam Inlet Conditions and

Turbine Mechanical Efficiencies (SI Units)

Table 29-4 Representative Condensing Turbine Heat Rates Under Various Steam Inlet Conditions and

Turbine Mechanical Efficiencies (SI Units)

Inlet Condition

Steam

Theoretical

Heat Rate

Heat Rate

Heat Rate

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