Cost of Fire Tube Boiler

Fire tube boiler also known as boiler shell boiler. The basic structure is to install a small cylinder, tube (called “fire tube”) or other shaped shell (called “furnace”) in a large cylinder (pot shell). The fire tube is isolated from the large cylinder and forms a jacket. The jacket contains water, and the fire tube and the furnace tube serve as a combustion chamber and flue. The flue gas generated by the combustion of the fuel flows through the fire tube or the smoke tube, and heats the water, steam or steam-water mixture outside the fire tube or the smoke tube.

Fire tube boiler is divided into three types: fire tube boiler, smoke tube boiler and fire tube smoke tube boiler.

1. Fire tube boiler

The fire tube boiler is mainly composed of a larger diameter drum and a smaller diameter fire tube. As the volume of water or steam between the pot and the fire tube, the fire tube is both a stove and a flue gas passage.

2. Smoke tube boiler

The smoke tube boiler is improved on the basis of the fire tube boiler. Many tubes are used in the pot instead of the fire tube to increase the convective heat transfer surface. In order to increase the heating surface, the combustion chamber of the smoke tube boiler can be arranged outside the drum and built with refractory bricks. In order to make the structure compact and easy to move, a horizontal smoke tube boiler, such as a locomotive boiler, the combustion chamber can be arranged in the drum.

3. Fire tube smoke tube boiler

If the fire tube and the smoke tube are all arranged in the drum, it will become a fire tube smoke tube boiler. The fuel is burned in the fire tube, the flame enters the combustion chamber backward, and the flue gas is guided to the smoke box in front of the furnace through the smoke pipe, and then discharged from the chimney. Most ships using steam as power source use this kind of boiler, so it is also called ship boiler. The fire tube boiler has the advantages of compact structure, simple and even no furnace construction, easy installation and movement, large relative water capacity, good load change adaptability, water circulation channel not easily blocked by scale, and safer work. Because all or most of the heating surface of the fire tube boiler is arranged in the drum, to increase the capacity and pressure of the boiler, the diameter and wall thickness of the drum must be increased, and the amount of metal used is greatly increased.

Therefore, the capacity and pressure of fire tube boilers are greatly restricted. Generally, the evaporation capacity does not exceed 10 t / h, and the pressure does not exceed 2 MPa. Due to the limitation of the boiler drum, the heating area of the boiler is small, so the exhaust temperature is high and the boiler efficiency is low, generally not more than 70%. The metal utilization rate of fire tube boiler is up to 10t / t steam.

According to the above characteristics of fire tube boilers, fire tube boilers are widely used in small and medium-sized factories, heating and mobile equipment such as locomotives and ships.