Firetube boiler

Note BD — blowdown, BW = boiler water, CR = condensate return, FT — firetube boiler, FW — feedwater, HW = hot water, PF — pulverized fuel, PV = pressure vessel, SV = safety valve, TDS = total dissolved solids, WT... 

A 20-hp (approximately 5 gallons of liquid fuel feed per hour) firetube boiler has been installed in the Combustion... 

The combustion test program of synthetic liquid fuels is being conducted in a 20-horsepower (hp) firetube boiler and associated equipment. The system consists of a 20-hp, Johnston, three-pass, firetube boiler designed to transfer roughly 670,000 Btu/hr to the water side a water treatment and feed system a fuel holding tank and transfer pump and a stack exhaust duct equipped with numerous sample ports for gaseous and particulate emissions testing. 

Operating data for firetube boiler over 16 months ... 

The heat-transfer coefficient of the gas dominates the overall heat-transfer coefficient. For firetube boilers and heat exchangers wffiere the gas flows inside the tubes ... 

ASME PART PFT SECTION I - Requirements for firetube boilers. 

Firetube boilers are compact, low in initial cost, and easy to modularize based on plant requirements. Firetube boilers usually range in size from less than 2 to 50 million Btu/hr. Most industrial firetube boilers are either of horizontal return tube (HRT), scotch marine, or firebox type. 

Firetube boilers may be directly fired with waste fuels, either liquid or gaseous. They also serve to recover heat from incinerators fired on waste fuels. 

Watertube boilers can withstand much higher operating pressures and temperatures than firetube boilers. In addition, the watertube boiler design is safer. They can also bum a wide variety of fuels as well as wastes and have the ability to expand and contract more easily than firetube boilers. The major drawback is that watertube boilers are more expensive to install. The also require more complicated furnaces and repair techniques. 

In the firetube boiler (Fig. 6.4), the flame and products of combustion pass through the tubes. The heated water or other medium surrounds the internal furnace and the tube bundles. 

Various types of furnaces are used in conjunction with firetube boilers. Some are long, cylindrical tubes while others are firebox (Fig. 6.5) arrangements allowing the burning of solid fuels. In most cases, the firetube boiler includes a shell to contain the water and steam space. Within the shell will be tube sheets and tubes which are portions of the pressure vessel containment. The furnace or firebox provides space for the combustion process from the heat source. 

FIGURE 6.4 Firetube boiler. (Cleaver-Brooks Division.)... 

Many types of firetube boilers are being supplied to industry. One type is the horizontal return tubular boiler (Fig. 6.6). In this unit, the products of combustion travel across the shell and back through the tubes within the pressure vessel. These units are usually horizontally brick-set. 

Flue Gas - — — — E — E steck gas bom firetube boiler burning 4D oil (4% sulfur cwtent) m cyclic operation... 

Samples produced by a 6 MW pilot fluidized bed boiler and a pulverized coal fired 10 MW firetube boiler have been analyzed. It can be concluded that ... 

The most notable part of the traction engine made from copper is the boiler and its firetubes (see Fig. 1.1). In full size this would have been made from mild steel, and the use of copper in the model is a nice example of how the choice of material can depend on the scale of the structure. The boiler plates of the full-size engine are about 10 mm thick, of which perhaps only 6 mm is needed to stand the load from the pressurised... 

In the above example, a relatively complex steam generator of the watertube type has been adopted. Where lower-quality steam for process or fuel heating is required, a simpler shell (or firetube) design may be appropriate. In some cases, supplementary firing may be provided for the boiler, so further increasing plant complexity and with it the need for enhanced control and maintenance requirements. 

The table summarizes observations about a firetube waste-heat boiler made over a period of time. (Ti and Tj are the inlet and outlet temperatures of the hot fluid, in T.)... 

Miller, C. A., Linak, W. P., King, C. and Wendt, J. O. L., Fine particle emissions from heavy fuel oil combustion in a firetube package boiler. Combust. Sci. Technol. 134, 477-502 (1998). 

Characteristically boiler types are generally classified as either firetube or watertube. 

Another type of firetube unit is the Scotch marine boiler. This design was developed originally for shipboard installation. This type of boiler can be fired with either solid, liquid, or gaseous fuels. 

Another type of firetube unit currently being marketed is the vertical-type boiler. In this particular unit the fuel or heat source is in the bottom, and the products of combustion rise up through tubes and are emitted from the top of the unit. 

Packaged Firetube Engineering Manual, American Boiler Manufacturers Assodation, 1971. 

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