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

摘要

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.