TABLE OF CONTENTS Battelle has provided a well-written report that discusses power plant coal utilization in great detail. It gives a thermal efficiency of 80 83% for steam generation plants and 37 38% thermal efficiency for power generating plants at base load (about 70%). A base load plant designed for about 400 MW and up will run at steam pressures of 2,400 or 3,600psi and 1,000 F with reheat to 1,000 F and regenerative heating of feedwater by steam extracted from the turbine. A thermal efficiency of 40% can be had from such a plant at full load and 38% at high annual load factor. The 3,600psi case is supercritical and is called a once-through boiler, because it has no steam drum. Plants designed for about 100-350MW run around 1,800psi and 1,000 F with reheat to 1,000 F. Below 100 MW a typical condition would be about 1,3 50psi and 950 F with no reheat. Below 60% load factor, efficiency falls off rapidly. The average efficiency for all steam power plants on an annual basis is about 33%.
Locklin, D. W., Hazard, H. R., Bloom, S. G., and Nack, H., "Power Plant Utilization of Coal, A Battelle Energy Program Report," Battelle Memorial Institute, Columbus, Ohio, September 1974.
Three basic parts of boiler controls will be discussed:
Level control
Firing control (also applies to heaters)
Master control
For steam drum level control, the modern 3-element system steam flow, feedwater flow, and drum level should be selected. Steam and feedwater flows are compared, with feedwater being requested accordingly and...
