700 MW Steam Boiler Specifications

Boiler Basics

• The 700 MW steam boilers built by Mitsubishi vary in design but typically have a once-through system where water enters at the bottom and steam leaves the top. The combustion system is a circular firing method that reduces nitrous oxide emissions. The units run on coal power.

Steam Specifications

• The steam flow rate for Mitsubishi's 700 MW furnace is about 4,400,000 pounds per hour. At the outlet, the steam is under 3,625 pounds per square inch of pressure and between 1,000 to 1,100 degrees Fahrenheit. The temperature of the steam is controlled by adjusting the ratio of fuel to water or increasing airflow to the unit.

Auxiliary Components

• Auxiliary units on the 700 MW steam boiler include a coal pulverizer, fans and the nitrous oxide emission reduction system. Three types of fans on the unit each have variable blade pitch and include a forced air draft fan, primary air draft fan and induced air fans. The nitrous oxide system is a dry catalytic nitrous oxide scrubber.

Efficiency

• The efficiency of the 700 MW steam boiler is determined by the amount of carbon left in the coal ash. For the Mitsubishi boiler, the ash contains only 3 percent carbon. The goal for nitrous oxide is emissions that contain less than 140 parts per million (ppm) nitrous oxide. The Mitsubishi boiler's emissions range from 90 to 130 ppm.