Comparison between ZOZEN gas-fired fire tube boilers and water tube boilers

Fire tube boilers (also known as shell boilers) and water tube boilers are two main types of industrial boilers. Users select fire tube boilers and water tube boilers for specific applications. To purchase an appropriate boiler type is not an easy task because it is hard to say which type of boiler is better. Fire tube boilers and water tube boilers both have their own advantages and disadvantages. Having an in-depth understanding about the differences between the two types of boilers can help you make a right purchasing decision.

What is a fire tube boiler?

In a fire tube boiler, the threaded smoke tubes are surrounded by water. While passing through the threaded smoke tubes, the high temperature flue gas heats the water or vapour and ultimately produces steam or hot water.

ZOZEN WNS series fire tube boilers

Capacity: 1-20 t/h (0.7-14MW)
Pressure: 0.7-2 Mpa

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What is a water tube boiler？

The operation mode of a water tube boiler is exactly the opposite of that of a fire tube boiler. A water tube boiler is such a kind of boiler where the water is heated inside tubes and the hot gas surround them.

ZOZEN SZS series water tube boilers

Capacity: 20-110 t/h (7-116 MW)
Pressure: 1.25-5.3 Mpa

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Parameter comparison table of ZOZEN fire tube boilers and
ZOZEN water tube boilers:

Parameter comparison

Product model:: Fire tube boilers; Water tube boilers

Applicable fuel:: Natural gas, coke oven gas, blast furnace gas, carbon black off-gas, methane, diesel, light oil, heavy oil, etc.

Thermal efficiency:: More than 98%

Capacity range:: Steam：1 - 20 t/h
Hot water：0.7-14MW; Steam：20 - 110 t/h
Hot water：7 - 116 MW

Pressure range:: 0.7 - 2 Mpa; 1.25- 5.3 Mpa

Delivery mode: Packaged mode; Packaged mode：
20-35t/h（7-29MW）
Shop assembled mode：
40-55t/h （46-58MW）
Field assembled mode：
more than 55t/h （70MW）

Advantages and disadvantages of fire tube boilers and
water tube boilers

Advantages：

Disadvantages：

Simple structure, compact size, easy to install, low production and construction costs.
Low failure rate, easy maintenance, low maintenance and operation costs.
The use of ZOZEN high efficient threaded smoke tubes prolongs the staying time of flue gas and effectively improves the thermal efficiency.
The use of a large-diameter corrugated furnace reduces the thermal stress of the boilers. With sufficient steam storage space and heating surface, the boilers can produce high thermal power and high quality steam.

The capacity and pressure of fire tube boilers are limited by boiler structure. Generally, the capacity is lower than 20t/h and the pressure is lower than 2Mpa.
Owing to the large water volume, the time required to increase steam pressure is relatively long. And the boilers can’t make quick response to continuous large load changes.

Advantages:

Disadvantages：

Water tube boilers have large capacity which can withstand higher pressure and temperature. The maximum capacity has reaches 110t/h.
Water tube boilers can produce steam quickly and produce saturated or superheated steam according to actual requirements. Meanwhile, with good adjustment abilities, the boilers can precisely track load fluctuations.
The heating area of water tube boilers is the surface of tubes placed in the furnace instead of the boiler drum, which has good heat transfer effects and safety performance.
The boilers adopt membrane water wall structure. The reasonable design of the size of drum and steam-water separator can increase the steam quality.

Complicated structure, large volume, high manufacturing and maintenance costs.
Water tube boilers should adopt water treatment equipment to avoid the problems caused by boiler scale.

Conclusion:

Fire tube boilers and water tube boilers both have their own advantages and disadvantages. Enterprises can select the appropriate boiler type according to their actual requirements, such as the steam demand, boiler room area, boiler operation costs. As a leading industrial boiler manufacturer, ZOZEN has always devoted to providing customized boiler system for users. ZOZEN fire tube boilers and water tube boilers are widely used in all walks of life.