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Coal Furnace - Different Furnaces
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Are considering the installation of a coal furnace? For centuries, coal has been an important fuel and even now in the age of technology, it is still an important fuel. If you want to beat the winter chill, then a coal boiler or furnace will bring warmth into your home. Before we delve into the subject and understand different types of coal-fueld furnaces, here is a brief overview of coal and its importance.
What is Coal?
Coal is a widely used and abundantly available fossil fuel. According to estimates, America has coal reserves that could take care of our requirements of coal for the next three hundred years. Coal is of four different types, or ranks, i.e. lignite, sub-bituminous, bituminous, and anthracite. The amount of heat generated from a coal furnace depends on the amount and type of carbon in the coal used in the furnace. The higher the rank of coal, the more heat-producing energy it has. Lignite is ranked the lowest and has the lowest energy content. On the other hand, Anthracite contains 86-97% carbon and its heating value is marginally better than bituminous coal. Bituminous coal contains 45-86% carbon and has 2-3 times the heating value of lignite. So the ideal fuel for a coal burning furnace is either anthracite or bituminous.
Types of Coal Furnaces
There are various types of furnaces available for different applications. Broadly, you can classify coal-fueled furnaces into four categories:
1) Stoker
2) Cyclone
3) Pulverized
4) Fluidized-Bed
Stoker Furnace
The stoker furnace has a limited capacity and application. These furnaces can only be used to drive industrial processes and not for big power plants. In a stoker furnace, coal is introduced on a grate, and then it is burned on a stationary coal bed. There is ventilation below the burning bed from where the air comes in. The primary air initiates the process of combustion and at the same time cools the grate. A secondary airflow is maintained over the burning bed to complete the combustion process successfully.
Cyclone Furnace
The cyclone furnace can have as many as 16 combustion chambers. The central combustion chamber of this boiler works at a temperature of 3200°F. The cyclone coal furnace were used in the 1950s and 1960s but have been discarded since then because of its limitation related to burning low-sulfur coals.
Pulverized Coal Furnace
The pulverized coal boiler has a widespread use as it has the ability to burn all kinds of coal from anthracite to lignite. The furnace uses finely powdered coal air in a gaseous torch. The coal is pulverized by crusting and attrition to concert it into particles smaller than 0.3mm in diameter. The second advantage of a pulverized coal appliance is that it permits combination firing. However, this furnace produces large amount of fly ash because of pulverizing. The toughest part is maintenance of the the furnace. Moreover, the pulverizer requires a lot of power for pulverization of coal, which makes the process complicated and expensive.
Fluidized-Bed Furnace
The fluidized-bed furnace works on a process wherein the velocity of air is maintained in such a way that coal and limestone particles are suspended as if a boiling liquid. The main advantage of the fluidized-bed furnace is that it produces a higher rate of heat transfer. This reduces the furnace area and size. The combustion temperature is also lower than a conventional furnace. This furnace can also use high sulfur coal.
Based on the aforementioned, you can select a furnace that suits your requirements and budget. Taking an informed decision with expert opinion can be great help because coal furnace involves substantial initial and running expenses.
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