Factors affecting Coke rate in a Blast Furnace Jun29

Factors affecting Coke rate in a Blast Furnace...

Factors affecting Coke rate in a Blast Furnace  BF is a counter current reactor in which the reducing gas is produced by the gasification of the carbon of the BF coke with the oxygen of the hot blast injected via tuyeres in the lower part of the furnace. The reducing gas flows upwards reducing the iron bearing burden materials charged at the top of the furnace. Coke rate is the parameter for the consumption of BF coke which is measured in kilograms of BF coke consumed per ton of hot metal produced. Blast furnace (BF) coke is a key material for BF ironmaking, acting as a major energy source (fuel), a reductant, a carburization agent and a permeable structural support. There is no other satisfactory material available, which can replace, fully or partially, BF coke as a permeable support of blast furnace charge. BF coke is the most important raw material fed into the blast furnace in terms of its effect on blast furnace operation and hot metal quality. A high quality BF coke is able to support a smooth descent of the blast furnace burden with as little degradation as possible while providing the lowest amount of impurities, highest thermal energy, highest metal reduction, and optimum permeability for the flow of gaseous and molten products. Introduction of high quality BF coke to a blast furnace results in lower coke rate, higher productivity and lower hot metal cost. Role of coke in improving the BF performance is shown at Fig 1. Fig 1 Role of coke in improving BF performance A realistic assessment of the likely performance of coke in the blast furnace operating with or without injection technology includes those properties of coke that reflect its resistance to degradation under the chemical and...

Use of Iron Ore Pellets in Blast Furnace Burden Jun13

Use of Iron Ore Pellets in Blast Furnace Burden...

Use of Iron Ore Pellets in Blast Furnace Burden  Pelletizing is a process that involves mixing very finely ground particles of iron ore fines of size less than 200 mesh with additives like bentonite and then shaping them into oval/spherical lumps of 8-20 mm in diameter by a pelletizer and hardening the balls by firing with a fuel. It is the process of converting iron ore fines into ‘uniformed sized iron ore pellets’ that can be charged directly into a blast furnace. Fig 1 shows iron ore pellets. Fig 1 Iron ore pellets  There are several iron ore pelletizing processes/technologies available. However, currently, straight traveling grate (STG) process and grate kiln (GK) process are more popular processes. The physical properties of iron ore pellets are given below. •     Size – 8-20 mm •     pH (40 gm/L, 20 deg C; slurry in water) – 5.0 – 8.0 •     Melting point – 1500-1600 deg C •     Bulk density –  2.0 -2.2 t/Cum •     Tumbler index (+6.3 mm) – 93-94 % •     Abrasion index (-0.5 mm) – 5-6 % •     Compression strength (daN/p) – Around 250 •     Porosity – > 18 % The chemical analysis of iron ore pellets is given below. BF grade                     DRI grade Fe                                            %         63 – 65.5                       65 -67.8 SiO2 + Al2O3                         %              < 5                                 <5 CaO + MgO                            %           Up to 3                      Up to 0.10 P, max                                     %              0.05                              0.05 S, max                                     %              0.01                              0.01 Basicity, min                           %              0.5 Disintegration (-3.15 mm)   %                                                     2 Swelling Index                        %            13-18 Reducibility                             %                65 Different ISO standard tests for pellets are given in Tab 1 Tab 1 ISO standard tests used for BF pellets ISO standard test Measurement values Purpose ISO 4700 /Crushing strength  daN Pellet cold strength ISO 3271 /Tumble strength Fractions +6.3 mm...

Use of Nut Coke in a blast furnace Apr27

Use of Nut Coke in a blast furnace...

Use of Nut Coke in a blast furnace Metallurgical coke is produced during the carbonization of coking coal blend in a coke oven battery. This coke is produced normally in three size fractions namely coke breeze (size – 10 mm), nut coke (size +10 mm to – 25 mm) and blast furnace (BF) coke (+ 25 mm to – 80 mm).  BF coke is one of the most important factors which affect the economic efficiency of a blast furnace. It also constitutes a great portion of the production costs of the hot metal. The use of nut coke in blast furnace is the essential factor to reduce the costs of iron making. The consumption of the BF coke is strongly related to the CO2 emissions. History Earlier there was no use of nut coke in an integrated steel plant and it was sold to other users. Prof. V. I. Loginov suggested in 1960s to charge nut coke into the blast furnace in mixture with sinter.  Though this idea was successfully tested, yet there was initial resistance to use nut coke in blast furnace. In mid 90s Visakhapatnam Steel Plant started using nut coke in their blast furnaces and soon achieved a monthly specific consumption level of over 50 Kg/tHM. The blast furnace of Neelachal Ispat Nigam Limited which was commissioned in February 2002 achieved by 2004-05 a monthly average specific consumption level of over 100 Kg/tHM. Presently the use of nut coke in blast furnace as a substitute of a part of BF coke is considered as a proven technology and nut coke is being used extensively in blast furnaces all over the world. Modern blast furnaces use nut coke in different amount (10-140 Kg/tHM) and in different size of nut coke (10-40 mm)....