Pulverized coal injection method

Background

Iron is a fundamental metal for the way of life for most human beings, as it is abundant, which results in low prices, it can easily be extracted, and is easily modified due to its useful material property. After the industrial revolution (18-19th century), iron became a core material of industrial market, its importance was referred to in the phrase “iron is nation”, its productivity was directly treated as its national power. Therefore after World War 2, governments vigorously supported the growth of the iron industrial market; as a consequence, the action significantly contributed and influenced the development of the global economy. For its various uses, iron ore is extracted and smelted through the use of metallurgical furnace called a "Blast Furnace".

The Blast Furnace method is expected to survive for another century because of its efficient iron production rate at competitive costs with other iron making methods. Blast furnaces keep on improving by adapting with new technologies resulting from the rising global demand, yet the main chemical process remains same. But improvement of process does not mean solving the problems associated in uses of blast furnace. The rate of Iron production is highly influenced by the world economy which varies over the time and improving the operations efficiency can be considered one of major concerns for users of the blast furnace, however the biggest drawback of blast furnace operation is the inevitable carbon dioxide production from iron reduction processes, which is considered one of the major contributors in global warming. Nowadays, the Pulverized Coal Injection (PCI) method an internationally popular method for improving blast furnace operation.

Pulverized Coal Injection method

Pulverized coal injection (PCI) method was developed in 19th century, but this method was not implemented till the 1970s. Rise in concerns due to increased coke cost due to competition from accumulated demand for iron production and limiting resources, this method was attractive to iron making industries and increased its value.

PCI method is based on the simple concept of primary air (termed as conveying gas) carrying pulverized coal through a lance to the tuyere (mid bottom side inlet of blast furnace), then mixed with secondary hot air (termed as blast) supplied through a blowpipe in tuyere then piped to a furnace to create a balloon like cavity called a “raceway”, which then propagates coal, coke combustions and melts solid iron ore and reduces it to molten iron. The most remarkable property of this method was that this method allows for cheaper coal to be consumed in the system to replace expensive coke; as a result, it can remarkably cut down on costs. Due to severe environment inside the furnace, (>2000K), visual observations of raceway shape and size is impossible, therefore sensors regestering numbers are preferred to investigate the chemical and physical reactions inside the furnace.

Better understanding of the raceway and PCI method can optimize the performance of a blast furnace and reduce its cost. In recent years, further improvement of PCI method and the use of coal blend (mixing multiple different coals) injection methods are attracting industry.