Abstract: A method and means for improved control of the process for directly reducing materials containing iron oxides in a rotary kiln using a solid carbonaceous reducing agent, such as coal, introduced from the charge feed and discharge ends of the kiln, as the source of both fuel and reductant, and oxygen-containing gas introduced along the kiln length is disclosed wherein the portion of the reducing agent fed at the discharge end is blown as a stream in a prescribed manner into the discharge end of the kiln. In particular, the important features of the stream are described including its longitudinal distribution and axial spread over the charge bed, as well as its contact region with the kiln walls and the quandrants of the kiln barrel into which it is directed, whereby the bed and gas phase temperatures may be controlled and heat transfer to the bed enhanced.

Abstract: A method for maintaining the sulfur level below 0.05% by weight, and preferably below 0.02% by weight, in the DRI product from the process for directly reducing ore containing iron oxides in a rotary kiln using a solid carbonaceous reducing agent, fed at the materials feed end and at the discharge end of the kiln, as both fuel and reductant is disclosed, identifying the important factors in the process affecting the sulfur levels in the DRI and steps and means for properly controlling these factors.

Abstract: A method and means for improving the efficiency of the process for directly reducing ore containing iron oxide in a rotary kiln using a solid carbonaceous reducing agent, such as coal, introduced from the ore feed and discharge ends of the kiln, as both fuel and reductant, is disclosed wherein the charred coal or char found in the discharge product is recycled into the process at the discharge end of the kiln rather than the feed end as in the prior art. In particular, the recovered char, both coarse and finer particles, are transported to a recycle bin from which they are returned at a preselected rate to the kiln process by being injected along with the coal blown into the discharge end of the kiln. Alternatively, the recycle char alone may be fed without any coal at the discharge end of the kiln.

Abstract: A method and means for maintaining optimum operation of the process for directly reducing iron oxides in a rotary kiln, using a solid carbonaceous reducing agent, such as coal fed at both the charge feed end and discharge end as the source of fuel and reductant, and oxygen-containing gases is disclosed wherein the DRI product, charred coal or char, and fine waste found in the kiln discharge materials from the discharge end are separated and measured for fixed carbon content and the process parameters may be adjusted to optimum by establishing an appropriate percentage by weight, in the range from 5% to 15%, of fixed carbon in the total of these discharge materials.

Abstract: A method and means for improving the efficiency of the process for directly reducing ore containing iron oxide in a rotary kiln using a solid carbonaceous reducing agent, such as coal, introduced from the ore feed and discharge ends of the kiln, as both fuel and reductant, is disclosed wherein the charred coal or char found in the discharge product is recycled into the process at the discharge end of the kiln rather than the feed end as in the prior art. In particular, the recovered char, both coarse and finer particles, are transported to a recycle bin from which they are returned at a preselected rate to the kiln process by being injected along with the coal blown into the discharge end of the kiln. Alternatively, the recycle char alone may be fed without any coal at the discharge end of the kiln.

Abstract: In the direct reduction process for reducing iron ore to sponge iron of the type disclosed in U.S. Pat. No. 3,890,138 to Hockin wherein all of the air supply tubes along the rotary kiln inject air toward the discharge end of the kiln it has been found that by reversing the direction of injection of the air from one or more of the tubes in the preheat zone of the kiln the condition of the off-gases can be considerably improved without affecting the process in the reduction zone and ultimately the quality of the resulting product and improved preheating of the kiln charge can be effected without the formation of undesirable kiln accretions.

Abstract: A method and means for improving control of the process for directly reducing ores containing iron oxide in a rotary kiln using a solid carbonaceous reducing agent, such as coal, introduced from the ore feed and discharge ends of the kiln, as both fuel and reductant, is disclosed wherein the temperature profile of the moving bed of solids is maintained such that the temperature is moderated to remain below the sintering temperature of the materials in the bed from the feed end zone for about the first two-thirds of the kiln length and the temperature is then maximized within sintering limitations in the working zone which is limited to about the last third of the kiln length. The temperature profile is controlled by regulating the volumes of air supplied to the kiln atmosphere from air injectors at spaced intervals along the length of the kiln, after establishing the appropriate proportion of coal steadily blown into the discharge end of the kiln for the particular process constituents being used.

Abstract: In the direct reduction process for reducing iron ore to sponge iron of the type disclosed in U.S. Pat. No. 3,890,138 to Hockin wherein all of the air supply tubes along the rotary kiln inject air toward the discharge end of the kiln it has been found that by reversing the direction of injection of the air from one or more of the tubes in the preheat zone of the kiln the condition of the off-gases can be considerably improved without affecting the process in the reduction zone and ultimately the quality of the resulting product and improved preheating of the kiln charge can be effected without the formation of undesirable kiln accretions.