Air Blast System for Blast Furnace Jan29

Air Blast System for Blast Furnace...

Air Blast System for Blast Furnace A blast furnace (BF) produces liquid iron (hot metal) by the reduction of ore burden with reducing gases. The reducing gases are produced by the reaction of oxygen with coke and coal. This oxygen is part of enriched hot air blast which is blown and distributed at the bottom of the BF through the straight pipes, blowpipes and the tuyeres. This set is connected to the main bustle pipe. The volume of air which is enriched with oxygen and blown for the process in the BF to take place is provided by the air blowers. These air blowers take the air from atmosphere and compress it to the required pressure. This compressed air which is at about up to 200 deg C temperatures after compression is enriched with oxygen and blown into the hot stoves where the temperature is raised up to 1.200 to 1250 deg C. This hot blast air is then taken to bustle pipe through hot blast main. Air blast systems of modern high capacity blast furnaces operate with blast temperatures of up to 1350 deg C and blast pressures up to 5 kg/sq cm (g). The whole process is typically shown in Fig 1. Fig 1 Schematics of typical air blast system The main components of an air blast system of a blast furnace consist of (i) air blower, (ii) cold blast main, (iii) hot blast stove along with its combustion system, (iv) hot blast main, (v) bustle pipe, (vi) blow pipes and tuyeres known as tuyere stocks, (vii) set of valves, and (viii) control instruments. The air blower is the first equipment in the air blast system. It is located in the blower house and is meant for providing cold air blast to the...

Generation of Hot Air Blast and Hot Blast Stoves Apr18

Generation of Hot Air Blast and Hot Blast Stoves...

Generation of Hot Air Blast and Hot Blast Stoves            A hot blast stove is a facility to supply continuously the hot air blast to a blast furnace. Before the blast air is delivered to the blast furnace tuyeres, it is preheated by passing it through regenerative hot blast stoves that are heated primarily by combustion of the blast furnace top gas (BF gas). In this way, some of the energy of the top gas is returned to the blast furnace in the form of sensible heat. This additional thermal energy returned to the blast furnace as heat reduces the requirement of blast furnace coke substantially and facilitates the injection of auxiliary fuels such as pulverized coal as a replacement for expensive metallurgical coke. This improves the efficiency of the process. An additional benefit resulting from the lower fuel requirement is an increase in the hot metal production rate. All of these have a significant effect in terms of reducing the hot metal cost. History of hot blast stoves The use of blast furnaces dates back as far as early as fifth century B.C. in China. However, it was not until 1828 that the efficiency of blast furnaces was revolutionized by preheating them using hot stoves in conjunction with the process, an innovation created by James Beaumont Nielson, previously foreman at Glasgow gas works. He invented the system of preheating the blast for a furnace. He found that by increasing the temperature to 300 deg F (149 deg C), he could reduce the fuel consumption from 8.06 tons to 5.16 tons with further reductions with higher temperatures. In 1860, the cooperative use of hot stoves with blast furnaces was further transformed by Edward Alfred Cowper by recycling the top gas...