Effect of granulating characteristics on harmless disposal of waste selective catalytic reduction catalyst in iron ore sintering process

Abstract

The harmless treatment of waste selective catalytic reduction catalyst has become a thorny problem. In this investigation, a new method of harmless disposal of waste catalyst by utilizing iron ore sintering process is proposed, and the effect of granulating characteristics is studied. Results show that better bed permeability, shorter sintering time, and faster flame front speed could be characterized by applying higher granulating moisture. Sinter mineral and microstructure research found that wider distribution of skeleton‐crystal hematite while less calcium ferrite could be observed at higher granulating moisture. The porosity of sinter increases from 30.82% for granulating moisture 6.0% to 36.54% for granulating moisture 7.5% while the circle factor of pores decreases. Sinter index research results indicate that both tumbler index and yield have a descended trend whereas flame front speed increases with higher granulating moisture added. Productivity first increases then drops with increasing granulating moisture. Finally, a comprehensive index is used to evaluate the influence of granulating characteristics on sintering process, which first increases from 100 to 121 as granulating moisture increases from 6% to 6.5% then drops to 70.8 when granulating moisture further increases to 7.5%. The granulating moisture of 6.5% is recommended in present study.

Effect of coating structure of granulated quasi‐fuel particles in iron ore sintering

“…Figure 10 illustrates the microstructures of the four sinter samples. Four main components can be clearly observed in the mineral phase, namely, hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), calcium ferrite (CaO•Fe 2 O 3 ), and silicate 18,19,22,24 …”

“…Before the tests, all raw materials were divided by a rotary screen to ensure uniformity. The detailed chemical components and size distributions of the raw materials can be attained in our previous studies 18–21 . Table 1 gives the raw material composition of the sintering mix, which is a typical sintering blend in the Asia‐Pacific region 20,21 .…”

“…Figure 2 gives the granulation methods 18–21 . For base granulation, all ~110 kg of raw materials were dry mixed for 1 min.…”

“…Figure 3 illustrates the schematic diagram of the sinter pot test system 18,19 . The test system consists of the sinter pot, windbox, wet scrubber, and suction fan.…”

“…After sintering and cooling, a small piece of sinter at 300 mm of height was saved for mineralogy and microstructure characterization, which was considered as a typical sinter. The residual sinter was sieved into five groups (−5, 5–10, 10–16, 16–25, and 25–40 mm) and was weighted separately after dropped 4 times from 2 m height 18,19 . The total mass of all five groups of sinter was denoted as m 1 , and the sinter with +5‐mm particle size was recorded as m 2 .…”