750MW Balanced Draft, Pulverized Coal Fired, Radiant Boiler Furnace

PlantSim Unit #4 has a balanced draft Carolina type Radiant Boiler designed for pulverized coal firing. The unit has 54 dual-register burners arranged in three rows of inline burners each on both the front and rear walls.

The maximum continuous rating is 5,320,000 lb/hr of main steam flow at 2534 psig and 1005 F at the superheater outlet with a reheat flow of 4,410,000 lb/hr at 495 psig and 1005 F with a normal feedwater temperature of 541.8 F. Main steam and reheat steam temperatures are controlled to 1005 F from full load down to half load (3,368,900 lb/hr) by a combination of gas recirculation and spray attemperation.

The unit is designed for cycling service and is provided with a full boiler by-pass system. The unit can be operated with either constant or variable turbine throttle pressure from 63% of full load on down.

The design pressures of the boiler, economizer and reheater are 2975, 3050, and 750 psig, respectively.

Fossil Boiler Furnace Specifications

Boiler Furnace Type

Power Rating: 753 MWe
Babcock & Wilcox balanced draft, pulverized coal fired, once-through natural circulation boiler, horizontal opposed.

Steaming Rate

Steam delivered: 5,320,000 lbm/Hour (670 kg/sec)

Steam Conditions

Steam temperature at superheater outlet: 1005 F (540.6 C)
Steam pressure at superheater outlet: 2534 psig (17.47 MPa)
Steam temperature at reheater outlet: (1005 F) 540.6 C
Steam pressure at reheater outlet: 495 PSIG (3.4 MPa)

Efficiency

87.6%

Number of Burners

54 Dual Register Burners arranged in three rows of nine burners each on both the front and rear walls.

Pulverizer

6 Mills of type MPS-89GR

Coal Burning Rate

300 Tons/Hour

Air Heaters

One Primary and Two Secondary Ljungstrom

Primary Air Fans

Two centrifugal fans with variable inlet vane control.

Forced Draft Fans

Two centrifugal fans with variable inlet vane control

Induced Draft Fans

Four centrifugal fans with inlet damper control.

Recirculation Fans

One centrifugal fan with variable inlet vane control.

Flue Gas Temperature

261 F (127 C) at air heater outlet

Air and Flue Gas System

Two FD Fans, Two PA Fans, four ID Fans, and One Gas Recirculation Fan

A detailed simulation of the air and flue gas system is simulated, including two forced draft fans, two primary air fans, four induced draft fans, one gas recirculation fan, two pre-heaters, one primary and two secondary Ljungstrom’s air heaters and all damper and ducts associated with this equipment. The model responds accurately to the variations in temperature, flowrate and pressure of primary air, secondary air and flue gas.

Fuel System

Six Coal Pulverizes and Feeders

A detailed simulation of the fuel system includes dynamic calculation for the air pressure, pulverizer outlet temperature, and air and coal flow distribution.  The components simulated consist of six pulverizers, coal feeders, coal burners, hot air dampers, cold air dampers, and supplementary dampers and ducts.

Water-Steam Circuit

The water fluid circuit includes the condenser discharge that is pumped up to the drum through a series of pumps and feedwater heaters. The path consists of:

  • Two transmission driven condensate pumps
  • Condensate polisher
  • Steam packing exhauster
  • Five levels of low-pressure feedwater heating
  • Boiler feed pump, either electric driven start-up or turbine driven main boiler feed pump
  • Three levels of high-pressure feedwater heating
  • Economizer, integral to furnace, and upward to the drum
  • Feedwater entering the steam drum mixes with the existing saturated water and flows down through the downcomers located outside the boiler. Water from the downcomer is distributed to the furnace tubes via lower headers. Heat applied by radiation and convection to the furnace tubes causes boiling of the fluid in the tubes. Circulation will increase with heat input until the buoyancy difference equals frictional pressure drop and other losses. The saturated steam passes to the convection pass, enclosure wall, the primary superheater, the platen superheater, and the secondary superheater before it goes to the high-pressure turbine. Steam exhausted from the main turbine is reheated in the boiler, through 3 stages of reheating and supplied to the IP and LP steam turbines before being exhausted to the condenser.

    Electrical System

    The electrical system model includes the major loads on the 6.9kV busses; specifically, the motors for circulating water pumps, pulverizers, FD and ID fans, auxiliary cooling water pumps, condensate pumps, LP heater drain pump, primary air fans, gas recirculation fan, and standby boiler feed pumps. A breaker accomplishes generator synchronizing. All modes of synchronizing, i.e., manual, digital synchronizer and load control, and computer, are included. The excitation system model includes manual and automatic control of field current. Reverse power trip logic is also modeled. The electrical system is interfaced with the emulated operator interfaces for the DCS HMI and hard panel.

    During electrical system simulation, expected changes in voltage, current, active and reactive power throughout the system can be seen when breakers are closed or opened, motor loads are changed, generator is synchronized, and excitation and turbine power are controlled. Generator load angle (i.e., the phase angle of the generator induced emf relative to the generator terminal voltage- not available in plant instrumentation) is also calculated by the model. This can be monitored to understand the generator dynamics as the load and excitation are changed.

    Control System

    The control system is a simulation of the Bailey Infi90 control logic with approximately one hundred emulated operator displays and hard panels. Systems controlled include:

  • Unit Control
  • Turbine Control
  • Boiler Control
  • Fuel Control
  • Air Flow Control
  • Feedwater Control
  • Steam Temperature Control
  • Auxiliary Steam Control
  • Electrical System Control