252

Table 29-1 shows representative steam rates, in lbm/hp-h, under various inlet conditions, each at an exhaust condition of 3 in. HgA (10.2 kPa). Included are theoretical steam rates and actual steam rates with various steam turbine mechanical efficiencies. Note that D&S

Table 29-1 shows representative steam rates, in lbm/hp-h, under various inlet conditions, each at an exhaust condition of 3 in. HgA (10.2 kPa). Included are theoretical steam rates and actual steam rates with various steam turbine mechanical efficiencies. Note that D&S

refers to dry, saturated steam. Table 29-2 shows the same steam rates from Table 29-1 in SI units. Table 29-3 shows representative heat rates, in Btu/hp-h (HHV basis), under the same set of conditions shown in Table 29-1. Table 29-4 shows the same steam rates from Table 29-3 in SI

Fig. 29-18 Steam Turbine-Driven Process Compressor, with Gear Box in Drive Train. Source: Compressed Air and Gas Institute

Fig. 29-19 Multi-Stage Steam Turbine Process Compressor Drive. Source: Dresser-Rand

Fig. 29-20 45,000 hp (33,500 kWm) Steam Turbine Process Gas Compressor Drive. Source: Dresser-Rand

Fig. 29-18 Steam Turbine-Driven Process Compressor, with Gear Box in Drive Train. Source: Compressed Air and Gas Institute units. Heat rates are calculated under the assumption of 83 Btu/lbm (193 kJ/kg) hotwell enthalpy and 83% boiler efficiency in each case.

In topping-cycle applications, steam rates typically range from 20 to 55 lbm/hp-h (12 to 34 kg/kWh). Since they use only a small portion of the energy flowing through the turbine, topping-cycle applications depend on a large downstream thermal load. Since net efficiency for a topping turbine will approach 100%, total system efficiency will be a function of boiler steam generation and net heat rate or energy chargeable-to-power (ECP) will range from 3,000 to 3,500 Btu/hp-h (4,200 to 5,000 kJ/kWh).

Table 29-5 shows representative steam rates, in lbm/hp-h, for non-condensing turbine operation under various inlet and exhaust conditions. Included are theoretical steam rates and steam rates for various turbine mechanical efficiencies. Table 29-6 shows the same steam rates from Table 29-5 in SI units.

Fig. 29-21 75,000 CFM Steam Turbine Driven Centrifugal Steam Compressor to be Applied in Mechanical Vapor Recompression Process. Source: Centrifugal Compressor Division, Ingersoll-Rand Company

Figures 29-17 through 29-22 show several types of steam turbine mechanical drive applications. Figure 29-17 shows a sugar mill in which multi-stage steam turbines are

Mechanical Vapor Recompression Evaporation Process

Vapor_

Liquid Separator n

Vapor Vapor

Recycled -Vapors

Evaporato

Condensate

Steam

Compressor

Condensate

Fig. 29-19 Multi-Stage Steam Turbine Process Compressor Drive. Source: Dresser-Rand

Fig. 29-22 Line Drawing Illustrating Operation of Steam Turbine

Driven Mechanical Vapor Recompression Process.

Source: Centrifugal Compressor Division, Ingersoll-Rand Company

Condensate used to drive two cane knife and six mill drives through reduction gears. These units, which have been in operation for 25 years, feature oil relay governing systems and produce 200% torque at stall.

Figures 29-18 through 29-20 show various steam turbine process compressor drives. Note the large 45,000 hp (33,500 kW) capacity of the system in Figure 29-20.

Figure 29-21 is a steam turbine-driven centrifugal steam compressor applied in a mechanical vapor recompression evaporation process in a brewery. An illustrative line-drawing of system operation is shown in Figure 2922. This single-stage compressor produces 75,000 ft3/m (2,100 m3/m) of compressed steam. In contrast to the mechanical drive system shown in Figure 29-18, in which the gear box is shown in the drive train, this unit is driven directly by the steam turbine without an integral gear box. The steam turbine is directly connected to the impeller of the compressor and compressor speed is matched to that of the turbine.

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