TYPES OF INDUSTRIAL, COMMERCIAL, AND INSTITUTIONAL (ICI) BOILERS<br />Prepared by:<br />Asst. Lect. Shahad Falih<br /><br />Information in this article focuses primarily on a broad class of steam and hot water generating units known as ICI boilers. Because of differences in their features and characteristics, ICI boilers can be classified in at least three ways. <br />• Boilers are commonly subdivided into water tube or firetube units. These designations reflect the way the water and combustion gases are designed to pass through the unit.<br />• Boilers are sometimes classified by their heat sources. For example, boilers are often referred to as oil-fired, gas-fired, coal-fired, or solid fuel-fired boilers. Coal-fired boilers can be further divided based on the equipment used to fire the boiler. The three major coal-fired boiler subclasses are pulverized-coal (PC) fired, stoker-fired, and fluidized-bed combustion (FBC) boilers.<br />• Boilers are occasionally distinguished by their method of fabrication. Packaged boilers are assembled in a factory, mounted on a skid, and transported to the site as one package ready for hookup to auxiliary piping. Shop-assembled boilers are built up from a number of individual pieces or subassemblies. After these parts are aligned, connected, and tested, the entire unit is shipped to the site in one piece. Field-erected boilers are too large to transport as an entire assembly. They are constructed at the site from a series of individual components. Sometimes these components require special transportation and lifting considerations because of their size and weight.<br /> The basic purpose of any ICI boiler is to convert the chemical energy in fuel into thermal energy that can be used to generate steam or hot water. Inside the combustion chamber, two fundamental processes must occur to achieve this objective. First, the fuel must be mixed with sufficient oxygen to allow sustained combustion. The heated gases produced by the combustion process must then transfer the thermal energy to a fluid such as water or steam. Various components inside the boiler are required to promote efficient combustion and heat transfer. Their design depends on factors such as the type of fuel and the method selected to transfer thermal energy. The ICI boilers are manufactured in a wide range of sizes to burn coal, oil, natural gas, biomass, and RDFs as well as other fuels and fuel combinations. Most ICI boilers are classified as either water tube or firetube boilers, but other designs such as cast iron, coil-type, and tubeless (steel shell) boilers are also produced.