BOILER OVERVIEW

TYPES OF HEAT

Latent heat Sensible heat Total heat Specific heat

COMBUSTION

Visual observation Combustion

Factors effecting Exhaust smoke

Stack gas testing CO2 vs CO

C + O2 -> CO2 + 14,100 BTU/lbm carbon

2H2 + O2 -> 2H2O + 61,100 BTU/lbm hydrogen

S + O2 -> SO2 + 4,000 BTU/lbm sulfur

------------------------------- 2C + O2 -> 2CO + 3,960

BTU/lbm carbon

CIRCULATION

Natural Density of Saturated Liquid vs Saturated

Vapor @ 300 PSI ρf = 52.9 lb/ft3, ρg = 0.647 lb/ft3

Forced Accelerated Radiation Convection Conduction

BOILER COMPONENTS

Steam Drum & internals Headers Water Drum Tube Sheet Wrapper Sheet Drumhead End Plate Dry Pipe Water screen tubes Waterwall tubes Desuperheater Dry pipe

Superheater Risers Downcomers Generating Tubes Bottom blow line Surface blow line Superheater vent line Economizer drain line Safety Valves

Steam drum Superheater Economizer

Soot Blower

BOILER CONSTRUCTION

Firebrick (to 3000F) Insulating Brick (to 2500F) Insulating Block (to 1500F) Plastic Refractory (to 3000F)

Purging boiler Boiler sliding feet

BOILER CASING AND REFRACTORY

Courtesy of E. Baumgart

EFFICIENCY

Waste heat boiler Economizer

ATOMIZERS

Rated by turn down ratio Turndown Ratio = Max oil flow /

Min oil flow Turndown Ratio = (Max

pressure / Min pressure).5

IE: FO pump output 300 psi, min pressure for atomization is 100 psi

Turndown ratio = (300/100).5 = 1.732

Steam and Air Best adjustment (turndown ratio) Uses steam that cannot be

recovered No fuel returns Steam & fuel both supplied FO supply pressures vary 8 to

350 psi

Pressure jet atomizer One or more atomizers used

to adjust firing rate of boiler Poor turndown ratio, as

pressure decreases, nozzle spray cone increases in angle

Rotary Cup Burner is spun by electric

motor Fuel is sprayed into inside of

cup, centrifugal force against cup walls

“fine spray” Good turn down ratio, not

best

FUEL OIL SYSTEM

Fuel Oil Storage Fuel Oil Settling

Tank Fuel Oil Pump

(positive displacement pump)

Filters / Strainers Heaters

Burners (top or front) Fuel atomizer Register (supplies

air)

BOILER OPERATIONS

Flame Peephole in furnace Color of flame

Incomplete combustion Dirty injectors Dirty boiler fuel tips Improper fuel temperature/pressure Excess air, pushes heat up stack Controlled by stack gas analysis (excess air and CO)

Smoke Black Smoke

Insufficient air Dirty burner Burner/injector tips wrong size Poor fuel atomization (check temperature & pressure)

White Smoke – unburned fuel particles in exhaust along with water vapor Excess air Bright white flame

Brown Haze – indicates good combustion Golden flame

Clear Stack – possible excess air

FEEDWATER

Delivered by feed pumps to boiler and economizer

Water level out of sight on gage glass High water level Low water level Loss of feed pump Tube leak