Coal fired steam boiler DZL4-1.6-AII Manual

4 ton coal fired boiler

4 ton coal fired boiler


DZL4-1.6-AII is a type of packaged boiler, which has the structure of three-pass, fire and water pipe combined. Both sides of the boiler are arranged with light pipe, water-cooling wall. Some ascending tubes are pulled towards the furnace, forming the heating surface of the furnace top. There are refractory materials at the bottom of the drum, so that it will not be radiated by the flame with high temperature. There are two paralleled convection gas passes arranged at the side downwards of the drum. The fractions of coverage of both the front arch and the rear arch are close to 80%, which is beneficial to the coal combustion. The adoption of new type, large block and chain grate realizes the mechanical combustion. The boiler is equipped with forced draft fan, induced draft fan, to operate the mechanical ventilation. Moreover, the slag remover is equipped, to realize the mechanical slagging. The complete controlling and monitoring instruments make the boiler safe and reliable.

4 ton coal fired boiler
4 ton coal fired boiler

The fuel falls from the coal scuttle to the grate, and then come into the furnace to burn. Passing through the upper side of the rear arch(i.e. the first pass), the flame comes into the combustion chamber, then, from the combustion chamber to the convection gas pass(the second pass), through the front smoke-box into the single-pass thread fire tube bundle(the third pass), then into the economizer, the dust collector. Finally, drawn by the induced draft fan, through the chimney, it is discharged into the air.

The safe and stable operational condition range: Thermal load: 70%-100%

2.4 Ton Coal Fired Boiler specifications

Rated evaporation: 4t/h
Rated working pressure: 1.6MPa
Rated steam temperature: 204°C
Feeding water temperature: 20°C
Cold air temperature: 20°C
Test pressure: 2.0MPa
Radiant heating surface: 11.5 m2
Convection heating surface: 75.5m2
The economizer heating surface: 43.2 m2
The active grate area: 5.5 m2
Exhaust gas temperature: 145°C
Excess air coefficient at exhaust site: 1.65
Design thermal efficiency: 79.3%
The boiler water capacity: 6.5m3
Metal consumption: Boiler proper 6685kg
Steel structure 5280kg
Grate 7479kg
Total electricity consumption: 41.25KW
Design fuel type: Second grade of bituminous coal
Coal consumption: 767kg/h

3.4 Ton Coal Fired Boiler Fuel requirements:

This boiler type is designed based on class Ⅱ soft coal. The fuel is supposed to meet the “technical conditions for coal used in chain grate boilers”. The coal’s granularity requires that use selected coal or coal with few fragments. Besides, the coal whose size is smaller than 3mm shall be less than 30% while the biggest particle shall be smaller than 30mm.

4.Water quality requirements:

The water should be chemical processed before get into the boiler according to the requirements of GB/T1576-2008”Water Quality for Industrial Boilers”. The details are as below:

5.Introduction to the structural design

The furnace and convection pass are made up from boiler drum and water cooling tubes at both sides. The front smoke chamber consists of 4 shed tubes and front tube plate. There is screw thread convection smoke tubes installed inside the boiler. The chain grate bears the whole boiler proper in the bottom part of the water cooling system so as to be a package boiler.

Water quality requirements
Water quality requirements

5.1Water cooling system pert:

The water cooling system consists of 3 natural circulation hoops. In order to lower the inlet smoke temperature of the front tube plate, we install water cooling tubes at both sides to make convection smoke pass to absorb the heat. The down pipes adopt tubes of φ133×6 while the ascension pipes adopt tubes of φ57×3.The header adopts tubes of 159×6.There are continuous blow down tank and periodical blow down tank in the drum and periodical blown down tank in the headers at two sides.
The boiler adopt 40 cast iron stream-lined economizer tubes which are L1200mm*Ф50.The feed water and smoke have counter cross layout. There are also platform handrails equipped with the economizer so it will be easy to maintain.
The feed water gets into the boiler after going through the economizer. A part of water will go through the front and back down pipes and go into the headers. And it will go through the ascension pipes to be separated by the drum. The rest of the feed water will be heated by the screwed pipes and turn to steam naturally. The steam in the drum will come out of the main stream valve. The bottom part of the drum which contact with the fire directly adopts thermal insulation material to guarantee the safety of the steam and water systems.
The furnace wall is made of light firebricks and refractory concrete with vermiculite concrete thermal insulation layer outside. While the outer ring of it are equipped with guard board layering with a neat look.

5.2 Combustion System

Combustion system include coal hopper, chain grate and gear box.
Block chain grate is adopted, less coal leakage, good ventilation effect, convenient loading and unloading. The length between four and rear axle of the grate is 4.255m, width is 1.51m .Side sealing is air-cooled type.

The part under grate is divided into 5 independent air chambers , air distribution is made according to the situation of combustion , the way of air inlet is tail bilateral air inlet , air shutter of each air chamber is double baffle control ,make the air chamber pressure substantially equally everywhere. Use the sliding grate cleaning device, so as to prevent leakage and air stringing between the grate wind chambers.

Coal hopper and coal gate are set in front of furnace to adjust the thickness of coal layer which is transported to chain grate, speed of chain grate is controlled by gear box.

6.Assort Auxiliaries

The model of auxiliaries refer auxiliaries list. When users select auxiliary by themselves, each auxiliary parameter cannot be lower than the parameter on the list that supplied by our factory. High altitudes, parameter selection of fan should be revised

7.Control System

Control instruments include water feed & water level alarm, low water level interlock protection, overpressure alarm &interlock protection etc. The control bin can be set according the personal need of customers.


Install in accordance with GB50273-2009 “Boiler installation construction and acceptance specification” and installation instructions of DZL type packaged water-fire tube steam boiler.


The maximum part transport size: 6010×3060×3380