Foster Wheeler Boiler and Its Types

The modern water-tube boilers are designed by Amec Foster-Wheeler (FW). These are D-type boilers and are used in marine propulsion systems such as large vessels, passenger liners, naval warships, and so on. It is classified based on general boiler principles, as shall be mentioned shortly.

Classification Based on Design/Water-tube Arrangement

Foster Wheeler boilers are classified as D-type boilers compared with A or O-type boilers. By D-type, it means that the water tubes are arranged in such a manner that the tube bank resembles a D-shape.

Its different versions include D, ESD I, ESD II, ESD III, ESD IV, and ESRD.

But what is the difference between D and ESD-type foster wheeler boilers? The difference between the two is governed by the position of the superheater, which defines the internal tube-setting of the boiler.

Basically, in the D-type, the superheater is located within the main tube-bank, which is not the case in the ESDs. In all ESD variations, the superheater is positioned beneath the economizer, external to the main tube nest, thereby forming a separate convection unit that is readily accessible for inspection, upkeep, and water washing.

It is shown below in Fig. 1.

cross sectional diagram fooster wheeler boiler
Fig. 01

The comparison between important D-type FW boilers is tabulated below.

SpecificationD-TypeESD IESD IIESD III
Capacity (kg/Hr.)
Final steam
Temperature (°C)
Design Pressure
Final Steam
Pressure (bar)

Classification Based on Final Thermal Conditions of Steam

Besides the D-type category, there is another classification of the Foster-Wheeler boilers based on the final thermal conditions of the steam. Proper to it, FW boiler classification is mentioned below.

  1. Subcritical Boilers: These are the typical Foster-Wheeler boilers that are used in power plants for electricity generation. They operate at a temperature below the critical point of water. (Table 2)
  2. Supercritical Boilers: These boilers make a somewhat sophisticated category of boilers on account of the high quality of steam used in large-scale industrial applications. They operate at temperatures above the critical point of water. For the thermal parameters of the final steam, go to Table 2.
  3. Ultra-supercritical Boilers: These are the most advanced forms of supercritical boilers. They produce extremely fine-quality steam with high evaporative capacity. They are equipped with cutting-edge boiler technology and instrumentation. (Table 2)
Temperature (℃)Pressure (MPa)
Subcritical FW Boiler374.1522.12
Supercritical FW Boiler53824.1
Ultra-supercritical FW Boiler59327.5
(Table 2)

Moreover, FW manufactures steam boilers based on exclusive combustion methodology. It also designs boilers according to the fuel consumed. Governed by such criterion, FW boilers can be further classified thus:

Circulating Fluidized Bed (CFBs) Combustion Boilers

Foster Wheeler CFB boilers use fluidized beds of sand for the suspension and burning of fuel, such as coal.

They are famous for their efficient performance, good thermal efficiency, and predominantly lower emissions such as CO, methane, and soot.

Moreover, these boilers fulfill the market’s demand for utility-size boilers compatible with a variety of fuel qualities ranging from low-grade high-ash-fuels, bituminous, and anthracite coals to those of top quality such as biomass as well as waste fuels.

During the past 30 years, Foster Wheeler constructed 350 boilers based on CFB technology, out of which 240 are made for coal and wastes-like heat sources for the coal mining industry.

Based on the principle characteristics of different fuels, although the designs and operation of the FW boilers vary quite little.

However, all these boilers use the same circulating fluidization combustion technique. In short, Foster Wheeler CFB boilers ensure high reliability and excellent operational performance.

Waste Heat Recovery (WHR) Boilers

These boilers, as obvious by their name, utilize the heat of the waste flue gases in the production of steam.

These are energy-efficient boilers. Foster Wheeler waste heat recovery boilers are famous worldwide for their excellent design, operation, and optimal control over emissions.

In 2017, Amec Foster Wheeler designed and commissioned two waste heat recovery boilers that utilize waste heat from the gas turbine installed in Mexico, thereby increasing overall plant efficiency with no added fuel consumption.

Miscellaneous Industrial Boilers

These are the exclusive boilers designed by Foster Wheeler for miscellaneous industries such as petrochemical, chemical, oil refining, and so forth.