Energy Citations Database (ECD) - - Document #634651

http://www.osti.gov/energycitations/product.biblio.jsp?query_id=0&page=18&osti_id=634651[3/25/2013 12:40:24 PM]

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Formation of hexavalent chromium by reaction between slag and

magnesite-chrome refractory

Description/Abstract

Magnesite-chrome refractories have been used in steel, copper, and glass industries. The

service life of magnesite-chrome refractory varies with the process and serverity of

conditions to which it is exposed. Under normal industrial temperatures and oxidizing

conditions, Cr{sup 3+}, which is present in the refractory, can oxidize to Cr{sup 6+}. Spent

magnesite-chrome refractory is classified as a solid hazardous waste when it has over 5

ppm Cr{sup 6+}, because Cr{sup 6+} is solube in water and is known to be carcinogenic.

Iron and steel industries are increasingly conscious of this problem due to more stringent

environmental regulations. Therefore, bigger efforts have been made to recycle and

reduce solid wastes. The goal of this work was to understand how Cr{sup 6+} formation is

affected by the interaction between chromite phases present in magnesite-chrome

refractory and different slag compositions. In addition, the formation of Cr{sup 6+} as a

function of chromite particle size and cooling rate due to the chromite phase/slag

interaction was investigated. The following slag compositions were studied: calcium

aluminate, calcium aluminum silicate, and calcium silicate. It was found that the presence

of uncombined CaO in the calcium aluminate slags is responsible for a higher yield of

Cr{sup 6+}. However, the replacement of Al{sub 2}O{sub 3} by SiO{sub 2} in calcium

aluminate slags decreases the formation of Cr{sup 6+}. SiO{sub 2} reacts with CaO to

form stable 2CaO {center_dot} Al{sub 2}O{sub 3} {center_dot} SiO{sub 2} and CaO

{center_dot} SiO{sub 2} phases, consequently decreasing the amount of uncombined

CaO available to react with the chromite phase to form Cr{sup 6+}. Moreover, the content

of Cr{sup 6+} is decreased by increasing chromite particle size and increasing the cooling

rate of magnesite-chrome refractory.

Authors: Lee, Y.; Nassaralla, C.L. [Michigan Technological Univ.,

Houghton, MI (United States). Dept. of Metallurgical and

Materials Engineering]

Publication Date: 1998 Apr 01

OSTI Identifier: 634651

Resource Type: Journal Article

Resource Relation: Journal Name: Metallurgical and Materials Transactions B:

Process Metallurgy and Materials Processing Science; Journal

Volume: 29; Journal Issue: 2; Other Information: PBD: Apr

1998

Country of Publication: United States

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ADOPT-A-DOC?
Energy Citations Database (ECD) - - Document #634651

http://www.osti.gov/energycitations/product.biblio.jsp?query_id=0&page=18&osti_id=634651[3/25/2013 12:40:24 PM]

Language: English

Format: Size: pp. 405-410

Other Number(s): Journal ID: MTBSEO; TRN: TRN: IM9821%%101

Subject: 32 ENERGY CONSERVATION, CONSUMPTION, AND

UTILIZATION; PHASE STUDIES; MAGNESIUM OXIDES;

CHROMIUM OXIDES; CALCIUM OXIDES; ALUMINIUM

OXIDES; SILICON OXIDES; IRON OXIDES; REFRACTORIES;

SLAGS; CHEMICAL REACTIONS; WASTE MANAGEMENT;

METAL INDUSTRY

Update Date: 2009 Dec 16

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