Industrial boilers are closed vessels that use a fuel source to heat water or generate steam for industrial heating and humidification applications. Common fuel sources include coal, electricity, natural or propane gas, oil, steam or hot water, and wood. There are two basic types of industrial boilers: fire tube boilers and water tube boilers. Fire tube boilers channel hot gases through cylindrical tubes that are surrounded by the fluid (usually water) to heat. The boiler, which is the pressure vessel, contains the fluid. By contrast, water tube boilers channel water through tubes that connect to a steam drum and a mud drum. The upper drum heats the water and generates the steam. Fire tube boilers are less expensive than water tube boilers, but are not suitable for applications that involve pressures above 2,500 psig. Water tube boilers are available in larger sizes, feature faster recovery times, and can handle pressures up to 5,000 psig. Performance specifications for industrial boilers include heat output or capacity, maximum temperature, maximum pressure, and thermal efficiency.

Industrial boilers are available in several configurations. Cast iron boilers are suitable for low-pressure steam or hot water applications and typically range in size from 25 to 200 hp. Firebox boilers are similar to fire tube boilers, but use box-like instead of cylindrical attachments. Industrial boilers with steam generators transfer heat from the primary reactor coolant system to the secondary steam system without contaminating the secondary system. Radiant boilers, which feature a single-drum construction, are better suited for high-pressure applications than dual drum devices. Other types of industrial boilers include bubbling fluidized bed (BFB), circulating fluidized bed (CFB), and pressurized circulated fluidized bed (PCFB) systems. BFB units are particularly efficient when burning fuels with low heating value and high moisture and ash content. CFB systems provide for the cleaner combustion of fuels such as waste coals, petroleum coke, and even shredded automobile tires. PCFB industrial boilers operate with efficiencies that exceed those of many conventional power plants that fire pulverized coal. 

Industrial boilers are available with a variety of features. Some devices are certified by the American Society of Mechanical Engineers (ASME) or are designed for heating, ventilation, and air conditioning (HVAC) applications. Other devices include a de-aerator to remove dissolved air or an economizer to transfer heat from combustion gases to boiler feedwater. Low emissions industrial boilers are designed to reduce the release of sulfur oxide, nitrogen oxide and other emissions. Devices that include a safety valve prevent buildups of excessive amounts of pressure, while devices with a super-heater can heat steam above the saturation temperature. Industrial boilers are available with monitors or controllers and water treaters or conditioners. Some industrial boilers are mounted or are available in a packaged configuration.

Engineering Calculators Related to Industrial Boilers Pressure Loss in Straight Gas Lines Calculator