Dwight-Lloyd method
The Dwight-Lloyd process is used to sinter fine-grained ores (e.g. copper, lead or iron ore) into air-permeable granulate before the actual smelting process and to carry out a pre-reduction of the metal oxides of the ore.
history
The first machine to work according to this process was built by Arthur Smith Dwight (1864-1946) and Richard Lewis Lloyd in June 1906 in the copper mine in Cananea , Mexico, and in 1907 the corresponding patent was applied for. The two inventors, who founded the "Dwight and Lloyd Metallurgical Company" in New York in 1907, not only built a large number of these systems themselves, but also licensed the process worldwide, including to the system manufacturer Lurgi . The first machine to sinter iron ore using the Dwight-Lloyd process was built in the United States in 1910. The Bochum Association put the first Dwight-Lloyd sintering plant in Germany into operation in 1917.
functionality
In order to agglomerate fine-grained ores, which reduce the air permeability of the Möllers when smelting in a blast furnace , into coarse pieces , a mixture of ore and coke is placed on an air-permeable conveyor belt made up of lined up transport trolleys (the so-called "grate trolleys"). The ore-coke mixture is ignited by powerful gas burners directly behind the feed point. Air is sucked through the material through wind boxes underneath the grate wagons so that the reaction front eats its way from the inflamed surface to the grate wagons as it is transported on. At the end of the conveyor line, the fully sintered material is tipped off the grate trolley and can be fed to the blast furnace. In addition to sintering, which takes place between 800 and 1400 ° C depending on the type of ore, the ore has also already experienced a certain reduction, so that the efficiency of the downstream blast furnace is improved.
Up- and downstream, further improvements
Since the transport trolleys are exposed to a strong temperature load from the downwardly directed (“ downstream ”) combustion gases in the original process , the direction of flow of the air can also be reversed (“ upstream ”), although a thin starter layer of ore-coke mixture must first be applied the tape that is ignited - and only then the actual payload.
The Dwight-Lloyd process is still used today because it is one of the few continuously operating sintering processes that can be applied to a large number of different ores and is technically mature.
Literature and Sources
- Fathi Habashi: Principles of Extractive Metallurgy. General principles, Vol. 3: Pyrometallurgy Routledge, London 1969, ISBN 0-677-01770-7 ( online )
- Good description also in patent DE649527A from Fried.Krupp AG from January 10, 1934 and DE918116B from INDUSTRIAL AND FINANCIAL ASSOCIATION INC., Panama from August 15, 1952 (accessible via the DEPATIS system of the German Patent and Trademark Office )
- Joseph Newton: Metallurgy of Copper . John Wiley, New York 1942, pp. 59 ff ( online , accessed September 1, 2009)
- Harold E. Rowan: Development Of The Dwight-Lloyd Sintering Process . In: Journal of Metals , Vol. 8 (1956), pp. 828-831, ISSN 0148-6608 .
Individual evidence
- ^ Website of the Colorado Scientific Society online ( memento of the original from March 6, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (Accessed September 1, 2009)
- ↑ Julius H. Strassburger: Blast furnace-theory and practice, Vol. 1 . Gordon and Breach Science Publ., New York 1984, ISBN 0-677-13720-6 , p. 221 ( online )
