Steam power plant process conditions

Chromium is the most effective addition to improve the resistance of steels to corrosion and oxidation ar elevated temperatures, and Ihe chromium—molybdenum steels are an important class of alloys for use in steam power plants, petroleum refineries, and chemical-process equipment. The chromium content in these steels varies from 0.5 to Ill s. As a group, the low carbon chromium—molybdenum steels huve similar creep—rupture strengths, regardless of the chromium content, hut corrosion and oxidation resistance increase progressively vvith chromium content. Most of the chromium — molybdenum steels are used in the annealed or in the normalised and tempered condition some ol the modified grades have better properties in the quench and tempered condition. 

The concept of essergetic functional analysis is introduced as a tool for approaching a condition known as "thermoeconomic isolation" of the interdependent equipment components of a system or process. If an interdependent component is thermo-economically isolated, then that component may be suboptimized with respect to many new, underlying variables. The required essergy analysis procedures are illustrated by considering the synthesis and design of components of a large steam power plant. 

As a consequence, good, safe, steam-sampling points are required, and automatic, real-time continuous analyzer systems for monitoring of steam and condensate quality are very useful. These requirements usually are not a problem in larger power and process HP boiler plants. Here, each facility tends to have a unique combination of operating conditions and waterside chemistry circumstances that necessitate the provision of a steady stream of reliable operational data, and this can be obtained realistically only from continuous, real-time analysis. 

Your company produces small power plants that generate electricity by expanding waste process steam in a turbine. One way to ensure good efficiency in turbine operation is to operate adiabatically. For one turbine, measurements showed that for 1000 Ib/hr steam at the inlet conditions of 500 F and 250 psia, the work output from the turbine was 86.5 hp and the exit steam leaving the turbine was at 14.7 psia with 15% wetness (i.e., with a quality of 85%). 

However, it may be very difficult to supply power to the grid in case of a small chemical plant (even with WHRBs units) since enough steam may not be available steadily due to variations in process conditions. As a consequence, the turbines may not be able to generate steady and sufficient power for supplying to the grid. It may not be acceptable to grid authorities who generally want a steady supply. 

A cogeneration plant is using steam at 5500 kPa and 748.15 K to produce power and process heat. The amount of process heat required is 10,000 kW. Twenty percent of the steam produced in the boiler is extracted at 475 kPa from the turbine for cogeneration. The extracted steam is condensed and mixed with the water output of the condenser. The remaining steam expands from 5500 kPa to the condenser conditions. The condenser operates at lOkPa. Determine the work loss at each unit. Assume that the surroundings are at 290 K. 

Utility plants supply the required energy demands to chemical processes, namely, mechanical, electrical and thermal power (different levels of steam). Changes in specifications, composition of feed and seasonal product demands create several process conditions with the corresponding variation in the utility demands during one annual horizon. 

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