Abstract: Method and apparatus to determine the skin-temperature of heat-exchange tubes and to prevent overheating of the heat-exchange tubes in a process gas heater (where extreme conditions prevent obtaining sufficiently-accurate direct thermocouple or pyrometric measurement to reliably prevent such overheating) by calculating the maximum skin temperature of heat-exchange tubes using preferably real-time calculation of the overall heat flux through the walls of the heat-exchange tubes with preferably real-time values of gas composition and gas temperature at the inlet and at the outlet of the tubes to calculate the overall transferred heat; and by periodically measuring the temperature of the gas flowing through each of the heat-exchange tubes, and using the measured gas temperatures for calculating the skin-temperature of all tubes, or of a tube selected for the highest gas temperature using the equation: Q = 2 ? ? ? ? L ? ( Ts - Tg ) / ( ln ? ro ri Km ) .

Abstract: A processed DRI material having an average surface roughness (Ra) of less than 1.5 ?m is disclosed. A method and system for making processed DRI are also disclosed. One embodiment of the method and system may include assembling a rotatable chamber having an internal screen capable of supporting DRI during tumbling, with at least one opening in the chamber to permit fines to exit the chamber during tumbling, and delivering DRI into the chamber to tumble the DRI on the screen to remove fines from the DRI. Another embodiment of the method and system may include assembling a rotatable chamber having a feed end and an exit end, and having a screen therein capable of supporting DRI as the DRI moves through the chamber, and delivering DRI to the chamber and rotating the chamber to tumble the DRI while removing fines.

Abstract: A processed DRI material having an average surface roughness (Ra) of less than 1.5 ?m is disclosed. A method and system for making processed DRI are also disclosed. One embodiment of the method and system may include assembling a rotatable chamber having an internal screen capable of supporting DRI during tumbling, with at least one opening in the chamber to permit fines to exit the chamber during tumbling, and delivering DRI into the chamber to tumble the DRI on the screen to remove fines from the DRI. Another embodiment of the method and system may include assembling a rotatable chamber having a feed end and an exit end, and having a screen therein capable of supporting DRI as the DRI moves through the chamber, and delivering DRI to the chamber and rotating the chamber to tumble the DRI while removing fines.