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Showing posts with label DR Process. Show all posts
Showing posts with label DR Process. Show all posts

Direct Reduction (DR) Processes - First No Coke Option for Iron Making

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19-Dec-2009

The first no coke method of iron making units is Direct Reduction (DR Process). Direct reduction processes can be divided into those using non-coking coal (as in rotary kiln and rotary hearth furnace based processes) and those using natural gas (as in shaft furnace, fluidized bed furnace, and fixed bed furnace based processes). DR processes using coal have been found to be more suitable in areas, which have local sources of coal and ore but no natural gas. On the other hand in gas-rich areas, gas-based DR (larger in size and more energy efficient) is the automatic choice.

A large number of DR (direct reduction) processes are available today, which can be grouped as follows:
  • Coal based direct reduction (DR processes) using rotary kilns such as SL/RN, DRC, TDR, Jindal, Codir, Accar, SIIL and OSIL. 
  • Coal based direct reduction (DR processes) using rotary hearth furnaces such as Fastmet, Inmetco, Circofer and Sidcomet etc. 
  • Batch type gas based processes using retorts - HyL I. 
  • Continuous processes in a shaft furnace using reformed natural gas as the reductant such as Midrex and HyL III. 
  • Gas based processes using a fluidized bed - Fior, Finmet, Circored.  
  • Special processes for treating waste oxides such as Primus using a multi-hearth furnace.
We have described most of these DR (Direct Reduction) processes separately and individually in this Blog since, it will be too lengthy to put all of them at one place. To know more about each of the DR processes simply type the name of the process in the search box placed near the top of this Blog and search. Alternatively you may select and click on the name of the process from the list of KEYWORDS given in the sidebar.                 

MIDREX - The Most Widely accepted Direct Reduction (DR) Process of Ironmaking

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2-Oct-2009

Midrex the most widely accepted direct reduction (DR) process of ironmaking in the world was developed by Midland Ross Corporation of Cleveland, USA in 1967 , has the following distinctive features:
Recommended Natural Gas Composition for MIDREX Plants
Components
Vol %
Effects
CH4
C2H6
C3H8
C4H10
+C4 (Hydrocarbon)
CO2
N2
S
75 - 100
0 - 25
0 - 4
0 - 2
0 - 0.5
20 max
20 max
20 ppm.
(max Wt.)
--
--
Above 4% C3H8, water vapour content should be increased.
--

Above 20% CO2, export fuel is produced.
For every 10% of N2, fuel consumption increases by 2%.
Above 20 ppm, carbon deposition on catalyst.

MIDREX Process - Some Features
=> It allows the production of highly metalized DRI (exceeding 92%, see adjacent Table showing typical composition of Midrex DRI) and the carbon content of can be controlled in the range of about 1.0 - 2.0%.
=> Although originally developed for use with high grade pellets, the Midrex shaft furnace is now able to use some amount of lump ores. Optimum process conditions are often obtained by mixing 30-50% of an appropriate type of lump ore with high grade pellets. See adjacent Table showing Physical Characteristics of Pellets and Lump Ores used in the MIDREX Process.  
=> Fuel utilization in Midrex process has steadily decreased from an average of 12.5 - 14 GJ/t of DRI to 9.5 - 10.5 GJ/t. This improvement in energy efficiency has been the result of higher reduction temperatures, enrichment of reduction gas with methane, utilization of in-situ reforming, and pre-heating of the process gas utilizing waste heat from the reformer.
=> Following the advent of in-situ reforming, oxygen carriers from an external source are now not required in the production of reformed gas. Therefore, the investment cost and operating costs of Midrex units have been reduced.
=> The DRI produced is relatively active towards re-oxidation, particularly when moisture is present. Hence it must be deactivated if it is to be stored or transported over a long distance.    
Physical Characteristics of Oxide Feeds
(Pellets and Lump Ores) used in the MIDREX Plants

Pellets
Lump Ores
Screen analysis (wt %)
50 - 31.75 mm
31.75 - 6.3 mm
+ 15 mm
8 - 15 mm
– 8 mm
– 6.3 mm
Bulk Density (t/m3)
Compressive Strength (kg/pellet)
ISO Tumbler Test (wt%)
+ 6.3 mm
– 0.5 mm

--
--
10% max
85% max
5% max
--
2.0 - 2.1
270 min


95% min
4% max

5% max.
93% max.
--
--
--
7% max
2.0 - 2.6
--


--
--

Typical Product Composition of Midrex DRI
Content
Wt %
Fe (total)
Fe (metallic)
Metallization
SiO2
Al2O3
CaO
MgO
S
P
92 -93
84 - 88
93 - 95
2.0 - 3.5
0.5 - 1.5
0.2 - 1.6
0.3 - 1.1
0.005 - 0.015
0.02 - 0.04
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What is FASTMET Process of Ironmaking ?

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11-Sept-2009
Fastmet The Process Concept and References  
This is a direct reduction process using a Rotary Hearth Furnace (RHF) which was derived from the work done in USA by Midland Ross and Surface Combustion, in the ‘Heat Fast’ process, treated in 1960s. It is a solid reductant based process in which iron ore concentrate, pulverized coal and a binder are mixed together and pelletized. The resulting green pellets are fed either to a drier or directly to a rotary hearth furnace where the pellets are heated to 1250 - 1400OC and reduced to metallic iron. Burners and post-combustion the CO evolved provide the heat required to raise the pellets to the reduction temperature.
The first commercial Fastmet plant was commissioned at the Hirohata Works No.1 of Nippon Steel in April, 2000 and Hirohata Works No.2 in February, 2005 with material processing capacities of 190000 tpa each plant. The second plant established was Kobe’s Steel’s Kakogawa Works started from April, 2001 having a material processing capacity of 16000 tpa.  The Fastmet process has allowed the Kakogawa Works to achieve a zero emission rating of steel mill waste. Waste utilization is the principal application of the Fastmet process in Japan.       
FASTMET Process - Flowchart
Advantages of Fastmet


Some of the advantages of Fastmet process as have been reported are summarized as follows:
=> A wide variety of iron ore as well as steel mill wastes including BF dust, BF Sludge, BOF dust, Sinter dust, EAF dust, mill scale, and etc. can be used as the oxide feed.
=> Elimination of waste disposal cost and landfill liability as wastes is changed to a quality source of iron (DRI).
=> Recovery of Zinc contained in wastes (Zn deriving from scrap) which can be sold to zinc producer. Zinc removal: 95% or higher.
=> A wide variety of energy sources can be utilized including natural gas, LPG, coke oven gas, heavy oil, coke breeze and carbon bearing wastes or pulverized non-coking coal.
=> The short reduction time of less than 12 minutes enables easy plant starting and shut-down, and quick adjustment of production rate.
=> Reclamation of carbon is possible. Carbon contained in dusts will be used as reductant. The carbon content of DRI can be adjusted as per the customer’s requirement.
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