METHOD TO INCREASE THE BURNOUT OF PULVERIZED COAL INJECTED INTO BLAST FURNACE
Publication Date: 2010-Sep-07
The IP.com Prior Art Database
Coal Injected Into Blast Furnace
Summary of the Invention:
An improved injection method for the blast gas and/or coal stream in a blast furnace is proposed. The blast gas and/or the pulverized coal stream are injected tangentially or spirally to increase the residence time of the coal particles. The increased residence time for the coal particles will lead to significant devolatiliztion and higher particle temperatures and to increased char burnout in the raceway. This will lead to higher coal injection rates replacing the more expensive metallurgical grade coke.
Field of the Invention
The present invention relates to the injection of pulverized coal in blast furnaces. A method is proposed to either inject the blast gas or the coal carrying stream tangentially or spirally to increase the residence time of coal before it enters the raceway. An increase in residence time of the coal particles will enhance the devolatilization process and also the overall burnout of the coal. This will aid in increasing the injection rate of the coal to the blast furnace and further decrease the consumption of expensive coke. In conjunction with oxygen injection, it would improve the overall process in the blast furnace.
Description of the Prior Art
In a blast furnace, iron ore and coke are charged in alternatives layers which slowly react and move downward. The blast gas, usually enriched with oxygen, is charged at the bottom which moves upward providing the oxidant for the reaction with coke which in turns provides the energy for the reactions of iron ore. Metallurgical grade coke is an expensive raw material for the manufacturing of pig iron and there is a trend to substitute coal with the more expensive coke. The injection of coal has been implemented in a number of blast furnaces around the world, but it provides less energy compared to coke. In addition, the residence times of coal in the blast pipe are very short and are of the order of 20 milliseconds. As a result, most of the devolatilization and char burnout occurs in the raceway. This also results in fine particles which plugs the porous structure resulting into the channeling of the gases.
A typical blast furnace is shown in Figure 1. The blast air or gas is supplied through a number of blast pipes distributed evenly around the bottom of the blast furnace. Pulverized coal is injected into the blast gas in the blast pipe before the raceway. The gas is, usually, distributed through a single main to all the blast pipes. The pulverized coal and the carrier gas are injected downstream before the entrance to the furnace. The coal is carried to the furnace quickly providing very short residence time without any significant devolatilization.
Brief Description of the Drawings
Figure 1 shows the overall process for pig...