How does the fire tube boiler work?

How Does The Fire Tube Boiler Work?

As an important energy supply equipment, the fire tube boiler work can convert electric energy, chemical energy into solid or liquid fuels, and output high-temperature steam and high-temperature water with certain thermal energy through the conversion of the boiler equipment.

It is used in power stations, textiles, chemicals, building materials, and food, pharmaceutical, transportation, mining, and other industries are widely used.



steam boiler is a device that absorbs the thermal energy in the fuel and turns the medium (water) into steam. Steam meets design parameters such as pressure, temperature, volume, etc. Classified by function, steam boilers can be divided into two parts, combustion, and heating.

The former is used for the combustion of fuels such as bituminous coal, biomass particles, wood, rice husks, fuel oil, and gas, and the latter is used to generate water vapor.

2T Biomass Wood Chips Fired Steam Boiler with Chain Grate Stoker Low Pressure

Industrial biomass boiler (1)
SZL coal steam boiler

The working process can be briefly described as follows:

The fuel releases heat during the combustion process. After conversion, this heat is absorbed by the boiler’s heating structure, the water-cooled wall.

After the water is boiled, a large amount of steam is generated into the steam-water separation structure. The separated saturated steam continues to be processed by radiation, convection, etc., so as to meet the conditions of use of industrial equipment.

membrance wall

The high-temperature gas generated by the combustion is absorbed by the thermal energy recovery device and is subjected to a second cycle. After the temperature decreases, these exhaust gases are discharged from the chimney.


The steam boiler consists of three parts: water circulation, combustion system, and flue system.

  1. The water circulation system includes water supply equipment, economizer upper pot drum, lower pot drum, etc.
  2. Combustion equipment includes furnace, burner, coal hopper, grate, slag remover, etc.
  3. Flue equipment includes a chimney, air preheater, dust collector, desulfurization device, and other structures.

Circulation process of water circulation system:

From water supply equipment to economizer to upper drum to convection tube bundle to lower drum to lower header to the riser to upper header to the upper steam outlet.

Through this process, the water circulation is completed.

Structural advantages

(1) Simple structure, large steam volume, good adaptability to load.

(2) It has lower requirements on water quality and is mostly used for heating and heating of enterprises and households with low power requirements.

(3) At the same power, the volume is smaller than a water tube boiler.

(4) The furnace liner can adopt a three-pass vertical large furnace structure, which increases the area of the flue tube and the radiation heat absorption of the furnace.

(5) Large heating area, high thermal efficiency, sufficient water supply, and small boiler room area.

Technical parameters (taking coal-fired boilers 1-8T as an example)

DZL coal fired steam boiler
Model DZL1-1.0






DZL6-1.25(1.6) DZL8-1.25(1.6) DZL10-1.25(1.6)
Fuel  (AII soft coal) -AII -AII -AII -AII -AII -AII
Rated Capacity (T/H) 1 2 4 6 8 10
Pressure (Mpa) 1.0(0.7) 1.0(1.25) 1.25(1.6) 1.25(1.6) 1.25 1.25
Steam Temperature  ℃ 184(171) 184(194) 194(204) 194(204) 194(204) 194(204)
Input water temperature  ℃ 20 20 20 20 20 20
Rated radiating area  M2 4.21 6.43 10.55 16.95 22.14 25.8
Convection radiation

surface M2

20.68 39.23 90.45 134.87 158.86 200.38
Economizer heating area


9.66 16.56 16.56 53.13 104.64 130.8
Chain grate heating area


1.852 3.15 5.18 8.395 9.35 10.98
Fuel Soft Coal II Soft Coal II Soft Coal II Soft Coal II Soft Coal II Soft Coal II
18757 18757 18757 18757 18757 18757
Exhaust gas temperature

152(160) 163(163.8) 163.8(169.5) 163(169) 161(165) 160(162)
Fuel Consumption


170.74 330 676.27 866.39 1153.42 1620
Heat  Efficiency (%) 77.73 72 79.32 79.83 79.95 81












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