Red iron oxide pigment derivation from acid regeneration plant by-product hematite

In the iron and steel industry, spent pickling liquor from pickling lines is regenerated and the HCl obtained is reused. In the Spray Roaster type acid regeneration plants (ARP), red hematite powder is the by-product of this process. The annual production of hematite in Turkey is approximately 15,000 tonnes and usually sold for manufacturing ferrite with adding a low value to the steel producer company. The aim of this study is to present an industrially applicable method that will derivate hematite into red iron oxide pigment (riop) to create 20 to 30 times higher added value than selling for ferrite. In the study, Bayferrox 180 M brand riop, which is used intensively in the market, was determined as the target pigment and morphological, physical and chemical characterizations were made in parallel with hematite. Parameters such as particle size distribution, bulk density, amount of water-soluble substances, chloride content and pH value that need to be developed for hematite have been determined and process steps have been applied for each of them to reach the values suitable for use in coil coating paint. A comprehensive laboratory infrastructure, including SEM, XRD, ICP-OES, optical microscope, laser diffraction particle size distrubitor, color spectrophotometer etc., has been used in the work packages during the conversion of hematite into pigment for paint industry. Within the scope of determining the optimum grinding system and parameters, trials were made with 4 different laboratory type grinders. Although the problem of caking and adhesion is observed in other grinders, pigment grade particle size distribution with D97 value of 4.9 μm has been reached with suitable classifier speeds at 0.8, 3.0 and 7 bar grinding pressures with jet mill. The highest grinding efficiency of 23.5 kg / hour was achieved with 7 bar grinding air pressure and 3000 rpm classifier speed. Two different methods have been proposed to remove chloride and one of them, chloride removal by heat treatment method has been used in the study. The furnace suitable for the removal process of chloride has been designed, manufactured and used in all working processes with a capacity of 10 kg / hour. With this method, it was possible to reduce the amount of chloride from around 0.5% to 0.04% and all other parameters in the pigment specification were also captured. Polyester-based pigment paste prepared using both target pigment and red iron oxide pigment derivated from hematite (riopdh). Full-tone, white tint and RAL 3009 colored semimatte coil coting paints were produced from the paste on a laboratory scale. All the necessary performance tests were done on paints and on the panels obtained by application of these paints. Kansai Altan R&D center infrastructure was used to investigate the behaviors of the riopdh in the paint system and dry paint film. Although all results meet the requirements, some low performance comparing to the target pigment was observed in the dispersion of the riopdh in the rub out test. In accelerated aging tests, riopdh gave satisfactoring results. At the final stage after laboratory scale studies, 360 kg industrial scale RAL 3009 colored polyester-based semi-matte coil coating paint was produced at AkzoNobel Kemipol production facilities. 40 tons of galvanized coil has been produced in MMK Metalurji Color Coating Line (CCL) in accordance with commercial purpose by using the paint. It has been determined that all the test results of RAL 3009 Prepainted Galvanized (PPG) sheets meet the expectations of DIN EN 10169, the standard for Prepainted PPG products. In addition, the PPG sheets were exposed to natural aging test in light industrial environmental conditions at an altitude of 32 m at a distance of 642 m from the sea in Hatay region, Turkey. Changes in their color and brightness were monitored in every 3 months during 15 months. After 15 months, while the color value changed by 0.73 dE, PPG sheets managed to maintain 97.1% of the initial gloss.