Phosphorus partitioning and recovery of low-phosphorus iron-rich compounds through physical separation of Linz-Donawitz slag

The Linz-Donawitz（LD） steelmaking process produces LD slag at a rate of about 125 kg/t. After metallic scrap recovery, the non-metallic LD slag is rejected because its physical/chemical properties are unsuitable for recycling. X-ray diffraction（XRD） studies have indicated that non-metallic LD slag contains a substantial quantity of mineral phases such as di- and tricalcium silicates. The availability of these mineral phases indicates that LD slag can be recycled by iron（Fe）-ore sintering. However, the presence of 1.2wt% phosphorus（P） in the slag renders the material unsuitable for sintering operations. Electron probe microscopic analysis（EPMA） studies indicated concentration of phosphorus in dicalcium silicate phase as calcium phosphate. The Fe-bearing phases（i.e., wustite and dicalcium ferrite） showed comparatively lower concentrations of P compared with other phases in the slag. Attempts were made to lower the P content of LD slag by adopting various beneficiation techniques. Dry high-intensity magnetic separation and jigging were performed on as-received samples with particle sizes of 6 and 3 mm. Spiral separation was conducted using samples ground to sizes of less than 1 and 0.5 mm. Among these studies, grinding to 0.5 mm followed by spiral concentration demonstrated the best results, yielding a concentrate with about 0.75wt% P and 45wt% Fe.

"In-situ Recycling" :Monolithic Ladle Repair with Shotcreting

The service life of refractories in ladle walls is limited by corrosion,abrasion,thermal shock and structural spalling mechanisms. When the ladle is lined with bricks they typically need to be completely removed after a certain number of heats to be replaced by new bricks of the same size as the original bricks. Not so for monolithic ladle linings. At the end of their service life the remains of the castable can almost completely be recycled as they can in fact stay in place. Only the worn-out part of the lining has to be replaced by a new castable. 20%-50% of the initial ladle lining can be recycled ＂insitu＂. The installation can efficiently be done by shotcreting technics. But it requires a castable that resists slag penetration very well. Castables based on a calcium magnesium aluminate bond provide the required penetration resistance. Pumping and shotcreting is very well adapted for repairs of blast furnace shafts,torpedo cars,hot metal and steel ladle linings[1]. However,very little is published about how a good pumping and shotcreting performance can be achieved when the installation has to be done under extreme weather conditions. At high ambient temperature the challenge is to ensure a good pumping result without early castable stiffening. Blockage of the pump would be the consequence. At low ambient temperature the difficulty is to de-activate the highly efficient deflocculant fast enough with a gelling agent added intothe wet mix at the nozzle to prevent the gunned material slipping off the wall. This paper studies strategies how to achieve good installed properties even at extreme ambient temperatures. The interactions between deflocculants,retarders,gelling agents,and calcium magnesium aluminate binder as a function of temperature are studied for an alumina- spinel ladle castable. Beside a new gelling agent for this castable type also a special stabilizer to reduce the temperature sensitivity has been investigated. It will be highlighted how the use of the new calcium magnesium aluminate binder in ladle castables and shotcretes maximises their service life and minimises material consumption.

Melting Characteristics of Recycling Slag in Decarburization Converter and Its Application Effects

The steel slag in the decarburization converter is treated by the little water-spreading （ LWS ） and the heat-stewed （ HS ） methods , which is used as the furnace burden of the dephosphorization converter.The slag characteristics by the LWS and the HS methods and its application effects as the furnace burden are researched.The results show the moisture content in the HS slag is higher than that of the LWS slag.There is higher total iron content in the HS and the LWS slags and almost same melting point.The dicalcium silicate content in the LWS slag is higher than that in the HS slag.The tricalcium silicate in the LWS slag is lower than that in the HS slag.There are a lot of calcium ferrite in the LWS and the HS slags , which is beneficial to dephosphorization and slag melting.The LWS and the HS slags are added to dephosphorization converter each charge by 3or 6t.The results show that the saving lime is 0.7-1.0tfor each charge.The petrographic constitute of final slag for the dephosphorization converter by adding the LWS and the HS slags is dicalcium silicate , RO phase and glass phase.There are a little calcium ferrite phase in the LWS slag , which is helpful to dephosphorization.So there are better dephosphorization effects for the LWS and HS slags.