The auxiliaries breathe life into an otherwise static boiler made of pressure parts (PPs) and nonpressure parts (NPPs). The auxiliaries, generating and regulating the flows, are present in the following two circuits: 1. Air and gas circuit that comprises A. Fans B. Dust-collecting equipment C. Dampers 2. Steam and water circuit that comprises A. Feed […]

Except in the case of package boilers and small-field erected boilers of up to —50 tph, the boiler structure constitutes the heaviest single subgroup and contains the maximum number of subassemblies and individual parts. Pressure parts and firing equipment are distinctive to the boiler, whereas the structure defines the delivery schedule of the whole plant. […]

Fabricated parts of the boiler can be divided broadly into the following categories: 1. Unheated pressure parts (PPs) (coded parts kept mostly outside the gas pass) 2. Draft plant items (mainly sheet metal work) 3. Structures (mainly rolled and fabricated steel work) These parts do not participate in heat transfer, other than in the gas-swept […]

Economizer surfaces transfer heat from flue gases to pressurized andsubcooled FW on its way to the drum. Heat transfer in an ECON is nearly entirely by convection, and hence the gas velocities are maximized consistent with pressure drop and tube spacing limitations. Coal ash in flue gas at temperatures <600°C is no longer sticky and […]

Economizer and airheater are called the back-end equipment. They are the last of the heat traps and positioned behind the evaporator surfaces in bidrum boilers and behind SH/RH surface in radiant boilers. The ECON is so-called because it economizes the fuel usage by extracting the low-grade heat. Flue gases leave the evaporator in bidrum boilers […]

The efficiency of the steam cycle is improved by higher steam pressure and tempera­ture as well as reheating. Both superheating and reheating of steam have to be as high as possible. At a steam pressure of 120 bar and higher, the cycle efficiency improves by —1% for every 20°C rise in superheat. Therefore, high superheats […]

Boiler and evaporator surfaces are the HSs that are exposed to the flue gases on the outside and carry the steam and boiling water mixture on the inside. Furnace The furnace is the enclosure around the firing equipment, which provides adequate 1. Volume to permit completion of combustion, that is, to meet the residence time […]

A boiler is a plant in which essentially two processes are at work, namely, combustion and heat transfer. 1. Combustion to release heat from fuel in the firing equipment. 2. Transfer of the released heat to water and steam in the various heat traps of the boiler. Combustion and firing equipment of different types is […]

Wear is a progressive loss of material due to mechanical action such as continuous impingement of particles. For information on wear of boiler parts due to ash, please refer to 3.5.1.2.1. Corrosion is a chemical or electrochemical action, leading to loss of material, whereas wear is a mechanical phenomenon. Wear is prevented by protecting the […]

All the nonferrous parts of a boiler are known as BRIL, which is an acronym for bricks, refractory, insulation, and lagging. The boiler setting or enclosure, which is the assembly sur­rounding all the hot parts, is substantially made of BRIL so that 1. The heat is contained within the boiler. 2. Heat loss is restricted […]