xx5050 sieve size value which is smaller than 70 µm and a first specific surface area; and the step of increasing the first specific surface area of the particulate steel slag material to a second specific surface area which is higher than 5 m²/g by carbonating the particulate steel slag material by means of a gas comprising carbon dioxide. The flue gas is then contacted with at least a portion of the carbonated particulate steel slag material as said sorbent to capture said acid pollutants in the carbonated particulate steel slag material.
The present invention relates to a method for recycling waste material generated in a stainless steelmaking process in a stainless steel mill. Most of the waste materials are already recycled such the steel slag materials and the filter dust collected above the different furnaces. The refractory linings of the different furnaces and ladles used in the steelmaking process need to be replaced regularly and produce a considerable amount of spent refractories. A portion thereof can be reused to produce new refractory bricks but a large portion needs to be landfilled under controlled conditions due to their too high heavy metal content. An even larger amount of waste material is the particulate mixed waste material which is gathered from the floor of the steel mill. This material has also a too high heavy metal content so that it also needs to be landfilled. Due to their swelling properties, they are also not suitable for being incorporated in building materials. According to the invention, these fine materials are agglomerated into larger pieces and are introduced as slag former in the steel furnace. Due to their relatively high MgO content, they can be used to replace dolime and lime as slag former.
The carbonate bonded, press-moulded article is produced by press-moulding a particulate, carbonatable material that contains water and by carbonating the obtained compact with carbon dioxide gas. In order to be able to ensure an optimal compressive strength of the article two types of tests are provided. In the first type of test a sample of the particulate material is compressed with an increasing compaction pressure and when water starts to be expelled from the material as from a particular compaction pressure, the press-moulding step is performed with a compaction pressure which is at least 7 MPa smaller than this compaction pressure. In the second type of test different samples of the particulate material are press-moulded with different compaction pressures and, after having released the compaction pressure, the density of the compact is determined. In case this density decreases instead of increases as from a particular compaction pressure, the press-moulding step is performed with a compaction pressure which is smaller than this particular compaction pressure.
B30B 9/04 - Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using press rams
B30B 9/06 - Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using press rams co-operating with permeable casings or strainers
B30B 11/02 - Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses or tabletting presses using a ram exerting pressure on the material in a moulding space
C04B 28/02 - Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
4.
Method of treating an alkaline granular carbonatable material
The invention concerns a method of treating an alkaline granular carbonatable material which contains aluminium metal and which has in particular a pH of at least 10. The method comprises an oxidation step wherein at least a portion of said aluminium metal is oxidized by contact with moisture. The aluminium should be oxidized to avoid swelling problems when using the granular material as aggregate. In the method according to the invention this oxidation is accelerated by providing at least one oxidizing agent in said moisture, which oxidizing agent has a higher redox potential than the water contained in said moisture. The method further comprises a carbonation step wherein the granular carbonatable material is at least partially carbonated to lower the pH thereof. In this way the formation of ettringite, which may also release aluminium ions which causing further swelling problems, can be avoided in the granular material or any ettringite present therein can be destabilized.
C04B 18/00 - Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stoneTreatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
5.
Process for preparing a foaming slag former, product and use thereof
Process for preparing a foaming slag former for electric furnaces comprising the steps of aggregating solid slag particles into a coarser granular material and carbonating the solid slag particles to form the foaming slag former. The solid slag particles are preferably aggregated before carbonization, so that the carbonates form a solid matrix binding the particles together.
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