Suitability of Auger Pressing Briquettes for Blast Furnace Use Based on Laboratory Tests

Abstract

Briquetting is a process in which fine materials unsuitable for use as such are agglomerated to achieve a larger particle size. Auger pressing is a novel briquetting method to efficiently improve the recycling of by-products from iron and steelmaking. The high-temperature properties of auger pressing briquettes mainly consisting of blast furnace sludge and mill scale were evaluated. The aim was to determine the suitability of the briquettes for blast furnace (BF) ironmaking by studying the reduction, swelling, and cracking behavior using a laboratory-scale furnace. The blast furnace simulator (BFS) capable of performing non-isothermal reduction experiments with changing gas compositions was used to simulate the different stages of reduction up to 1100 °C in an atmosphere with N2, CO, and CO2 gases. A commercial olivine pellet and a conventional industrial BF briquette were used as reference samples. The sample weight losses were monitored by thermogravimetry, swelling as a change in the volume, and cracking by visual inspection. The samples were analyzed using microscopes and an elemental analyzer. Based on the BFS experiments, the briquettes proved to be a promising raw material for BF use. They were of a self-reducing quality due to their carbon content and showed reduction to metallic iron faster compared to the reference samples. The swelling was slight, and despite the minor cracking the structure of the briquettes did not degrade.

Effect of Biocarbon Addition on Metallurgical Properties of Mill Scale-Based Auger Pressing Briquettes

“…Varying amounts of biocarbon were used in the laboratory-scale briquette recipes. In our previous work, 10) the examination of the high-temperature properties reducibility, swelling and cracking, of laboratory-scale cold-bonded auger pressing briquettes was implemented by simulating BF conditions in a laboratory-scale furnace, aiming to achieve different reduction degrees of iron. In this work, the amount of the main raw material of the briquette, mill scale, was gradually decreased in the briquette recipes while the amount of biocarbon was increased.…”

“…A total of 2 000 tons of mill scale-based industrial briquettes with a diameter of 40 mm were produced using auger pressing technology. The agglomeration method introduced in our previous work 10) is one of the key cold-bonding briquetting techniques, along with vibro pressing and roller pressing. In this type of agglomeration, the briquettes are cylindrical and cut to their final length by gravity.…”

“…Testing The cold-bonded biocarbon briquettes studied in this work were manufactured in smaller batches under laboratory conditions using auger pressing equipment presented in the previous studies. [10][11][12] The briquette production procedure demonstrated in Fig. 1(a) consisted of mixing the dry charge, adding a binder, adding water, aging the charge, preliminary and final auger pressing, and drying the finished briquettes.…”

“…The cold strength properties of the cured briquettes were tested using mechanical crushing strength, drop strength and abrasion strength tests in the same way as in our previous work. 10) The mechanical crushing strength tests were carried out for 7 pieces of briquettes of each quality by crushing along the axis. The drop strength was tested by dropping 3 ± 0.15 kg sets of briquettes three times using a drop height of 2 m. The abrasion strength was tested for 13-16 kg sets of briquettes in a tumble drum as defined in ISO 3271:2015.…”

“…The Blast Furnace Simulator (BFS) is a high-temperature tube furnace which has been used in numerous previous works to study changes during reduction for iron ore pellets, coke, sinter and lump ore [15][16][17][18][19][20][21] as well as briquettes, 10,22,23) and was utilized in the BF atmosphere simulation phase of this work. The BFS is made of heat-resistant steel and was capable of simulating actual BF process up to 1 100°C.…”