Lafarge Canada Inc.

Philip Souza Zacarias

David Bridson Oates

John Graham Whellock

A synthetic slag is produced by melting the mineral content of an organic carbon-containing mineral, for example, oil shale or tar sands, with a source of lime such as cement kiln dust. The organic carbon, especially hydrocarbon, content of the mineral is oxidized by oxygen gas, which typically is derived from air or an air/oxygen combination, in an exothermic reaction and the heat generated provides the thermal energy for the reaction between the mineral content and the source of lime. In this way the gaseous products will typically comprise nitrogen, unreacted oxygen, water vapor and carbon dioxide, and heat energy can be readily recovered from the hot off gas products evolving during the combustion reaction. The synthetic slag may be pelletized and employed as lightweight mineral aggregate or milled, or atomized and then milled, to cement fineness to provide slag cement.

Use of organic carbon-containing minerals

Concrete's durability to freeze-thaw cycles is dependent on its level of air entrainment, the appropriate level of which is achieved with the aid of surface active or air entraining agents. These agents promote the fragmentation of large air voids into smaller ones and stabilize air voids in the concrete. The carbon matter found in fly ash when used as a pozzolanic component of concrete, adsorbs the air entraining agents, reduces the air voids and concrete's ability to withstand many freeze-thaw cycles. This invention teaches a process for a partial removal of the carbon from the coal ash, used in concrete, through a partial combustion of only a fine carbon fraction of the carbon residue of the coal ash responsible for adsorbing the air entraining agents, in a reactor with a controlled ignition system. The process of the invention thus limits the adsorption of the air entraining agents and improves the freeze-thaw properties of the concrete produced.

Carbon removal through partial carbon burn-out from coal ash used in concrete

A synthetic slag is produced by a high temperature combustion reaction between coal ash having a high carbon content, and a source of lime such as cement kiln dust. The carbon content of the coal ash is oxidized by oxygen gas, which typically is derived from air or an air/oxygen combination in an exothermic reaction and the heat generated is exploited in the melting process. In this way the gaseous products will typically comprise nitrogen, unreacted oxygen and carbon dioxide, and heat energy can be readily recovered from the hot off gas products evolving during the combustion reaction. The synthetic slag may be pelletized and employed as lightweight mineral aggregate or milled to cement fineness to provide slag cement.

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Mississauga, Canada

Philip Souza Zacarias