Power plants boiler steam

In a Rankine power plant, the steam temperature and pressure at the turbine inlet are 1000°F and 2000 psia. The temperature of the condensing steam in the condenser is maintained at 60° F. The power generated by the turbine is 30,000 hp. Assuming all processes to be ideal, determine (1) the pump power required (hp), (2) the mass flow rate, (3) the heat transfer added in the boiler (Btu/hr), (4) the heat transfer removed from the condenser (Btu/hr), and (5) the cycle thermal efficiency (%). 

Power plant boilers are either of the once-through or dmm-type design. Once-through boilers operate under supercritical conditions and have no wastewater streams directly associated with their operation. Drum-type boilers operate under subcritical conditions where steam generated in the drum-type units is in equilibrium with the boiler water. Boiler water impurities are concentrated in the liquid phase. Boiler blowdown serves to maintain concentrations of dissolved and suspended solids at acceptable levels for boiler operation. The sources of impurities in the blowdown are the intake water, internal corrosion of the boiler, and chemicals added to the boiler. Phosphate is added to the boiler to control solids deposition. 

Figure 3. The minimum of the unit cost of essergy T/S with respect to the output steam temperature T for the power plant boiler.

Example 4.12 Exergy analysis of a power plant A steam power plant operates on a simple ideal Rankine cycle (see Figure 4.18). The turbine receives steam at 698.15 K and 4200 kPa, while the discharged steam is at 40 kPa. The mass flow rate of steam is 3.0 kg/s. In the boiler, heat is transferred into the steam from a source at 1500 K. In the condenser, heat is discharged to the surroundings at 298 K. Determine the energy dissipated at each state. 

Repeat Example 11.11 for heating the water to its NBP, 212°F. This was the situation in the earliest steam power plant boilers. Suggest ways in which the problem of accumulation of sohds in the boilers could be dealt with. 

In a particular electric power plant, the steam leaving a steam turbine is condensed to liquid water at 41 °C (T ) and the water is returned to the boiler to be regenerated as steam. If the system operates at 36% efficiency,... 

As of the mid-1990s, many older conventional steam plants have been converted to combined cycle. The old boiler is removed and replaced by a combustion turbine and heat recovery steam generator. Although the cycle efficiency is not as high as completely new plants, substantial capital cost is avoided by the modification and reuse of existing steam turbine and auxiHary equipment. In many combined cycle power plants, steam is injected into the combustors of the combustion turbine to lower peak flame temperatures and consequendy lower NO. ... 

The combined cycle is also appHcable to dedicated power production. When the steam from the waste heat boiler is fed to a condensing turbine, overall conversion efficiencies of fuel to electricity in excess of 50% can be achieved. A few pubHc utihty power plants use this cycle, but in general utihties have been slow to convert to gas turbines. Most electricity is generated by the cycle shown in Figures 5d and 6d. 

With a steam turbine, the turboeompressors ean be readily matehed to the different plant operating eonditions. Under eontinuous load, this type of installation is powered by the steam resulting from ammonia eombustion. Consequently, an outside steam supply is needed for startup. This may be a separate boiler or another external souree with live-steam properties not neeessarily eorresponding to those obtained from the nitrie aeid plant. The steam turbine must be of robust design beeause of the different pressure and temperature levels. 

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