Stringing expanded

A power recovery train—occasionally called a string—(Figure 4-53) employing a turboexpander usually consists of four main elements or casings the expander, a motor-generator, an air blower, and a steam turbine. The steam turbine is used primarily for startup and often to supplement the expander for generation of energy. This topic will be discussed in more detail later in this chapter. 

Figure 4-55. Elliott hot gas expander installed in an FCC power recovery string rated at 42,000 hp (31,330 kW).

Figure 4-70 shows a four-body TPG train (string). As before, the expander supplies power to the generator. The steam turbine supplies power to the generator, provides startup power, and provides control for synchronization. The generator provides electricity, and the gear is used to allow the expander and steam turbine to operate at near optimum efficiency with the generator at its desired speed. 

The typical three-body TPG string is shown in Figure 4-71. With this arrangement the generated electricity is limited by the expander output. Additionally, both startup and synchronization must be accomplished by the expander instead of the steam turbine. 

The full FCC string is synehronized using the governor eontrols on the steam turbine. Synehronization of the three-body TPG string is aeeomplished through the eontrol system and large expander valves. 

The foregoing demonstrates that modern digital devices offer highly reliable, state-of-die-art microprocessor technology that controls turbomachinery strings, monitors operating data, stores data for subsequent evaluation, communicates to odier systems, and can expand with future technologies. 

Prevent runaway of the string in the case of a generator load loss. The large amount of available energy upstream of the expander must be dissipated. 

Figure 4-143 represents a computer-generated plot that demonstrates the effectiveness of eddy current brakes in preventing overspeed of the string. The lower curve assumes the butterfly valve characteristic is linear from 60° open to the closed position. The rate of closure is 3.25 sec. (Butterfly valves are normally used to throttle the expander inlet gas.)... 

The top curve of overspeed versus time demonstrates that the string will accelerate to 22% overspeed due to expansion of the gas trapped between the valve and expander nozzle ring. However, if an eddy current brake were part of the string, the acceleration of the string would be reduced to 11% overspeed. This would provide an important margin of safety. 

Where turbine-driven FCC eompressor strings are used, the expander-driven generator ean export eo-gen power for sale to a eommereial eleetrieal network. This arrangement is shown in Figure 4-146. 

For Main Air Blower serviee without a steam turbine in the string, the unit shall be started by first applying windage steam and then aeeelerating the train to rated speed using the eleetrie motor. After aehieving stable rated speed, the expander inlet valve will be... 

At the beginning of the EntityDictionaryDao, it defines a series of constants the size and the name of each entity dictionary. Using these constants, the code allocates the Java Collection objects so that the sizes of these Collection objects do not need to expand at runtime, which causes extra CPU cycles to be wasted. Following the sizes are String constants names that are used to look up each entity dictionary. The class also defines SQL statements that are used to query the entity dictionary as static variables and initialize them in a static block ... 

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