BLAST FURNACE : DETAIL STUDY

By | April 14, 2016

There are several furnaces in the world for casting metal.  Electric Arc furnaces, Cornwall Iron Furnaces and Blast furnaces are the most significant among the casting furnaces. Each of these furnaces has different approaches and different types of applications. They have many benefits in human life.

Blast furnace

A blast furnace is a smelting furnace used for smelting iron. This is the industrial process of smelting iron on a larger scale.  Besides, other metals like lead or copper can be smelted in this metallurgical furnace. However, it is mainly used for extracting iron.

Blast Furnace

                Fig 1. Blast Furnace

How does it work?

Fuel, flux and ores are continuously supplied in a blast furnace through the top of the furnace. Side by side, a hot blast of air is sent at the bottom. Sometimes, it is enriched with oxygen. This is blown mainly to the lower section of the furnace through a series of pipes. These pipes are called tuyeres. This is done to intensify the chemical reactions throughout the furnace. As the consequence of this, a turmoil goes in the furnaces that downwards the materials and slag. At the end products, it produces molten metal and slag. These are collected from the bottom of this furnace.

The function of a blast furnace is to reduce and convert iron oxides into liquid iron. It physically converts and chemically reduces iron ores into hot metal.

Structure

It is a large-sized steel stack lined with refractory brick. Into the top of it coke, iron ore, and limestone are put. After that preheated air is blown into the bottom. This process goes for 6 to 8 hours until the raw materials descend to the bottom. When the process is finished, the final products (liquid iron and liquid slag) go downwards. A blast furnace can run four to ten years after it starts its operation. However, it requires planned maintenance after a certain period of time. A regular maintenance gives it a long life. To meet these, various types of cleaning methods are applied.

The modern blast furnace is a vertical shaft furnace. These are used for producing pig iron from iron ore.  Nowadays, these are also employed for processing steel, lead, copper, and other metals.

                   Fig 2. Blast Furnace

History

China showed it first time to the world around 1st century AD. In the late 15th century around 1491, it spread from China to England. Probably, in the late 15th century, it came to Namur in Wallonia (Belgium). The then time, the charcoal was used as fuel. These helped them decrease ore to a semisolid mass of iron that contains a relatively small amount of carbon and slag. At that time, removing iron mass was very critical as it needed hammering continuously until the slag was removed properly or separated from the main metal.  After hammering for a long time, the wrought iron would come out. The efficiency of the process of preparation was further enhanced later in 1828 by the practice of preheating the combustion air.

The blast furnace is the first or the primary step in extracting steel from iron oxides. Nowadays, it has extensive uses in the industrial preparation of iron. Many iron industries use it for exacting wrought iron from the ore. This process can produce a huge amount of iron without spending much time and money for it.

In most of the places in the world other, barring China, there is no evidence of the proper use of the blast furnace. The other places in the world gave more emphasis on the direct reduction in bloomeries. However, people from those areas mistakenly called it blast furnaces. The bloomery is old a process invented in modern-day Xinjiang. In Europe, the blast furnace was used by the Greeks, Celts, Romans, and Carthaginians. Several examples are found in France. The materials are found in Tunisia. It suggests that the people of Tunisia used it.

Although little is known about it during the Dark Ages, the same process was probably followed in the then time.

Uses of modern blast furnace

In our present time, we find it in modernized form. It is used for reducing iron oxide in a chemical way. As it can extract iron on an enormous scale within a very short time, it has extensive uses in the industrial process.

 

Leave a Reply

Your email address will not be published. Required fields are marked *