Dry removal of coatings, graffiti and other soiling on flat or curved surfaces and process equipment

摘要

The carrier air flow is produced by vacuum in an open circuit passing through the hose system (20,28) and a sealed cover (25) placed against the surface (3) being treated. 0.01-1.0% of abrasive is metered by gravity and/or vacuum into the air flow and the mixture is accelerated from 20-80 m/s before being moved to-and-fro across the surface. Used mixture and dust is sucked away and the abrasive separated, dried and remetered back into the air flow. Independent claims are also made for: a) the process equipment; b) use of various particulate materials for removal of paint, graffiti and other soiling. PREFERRED FEATURES: Acceleration is effected in a straight tube (21) either with a diameter reduction of 0.3-0.9 times the hose diameter (d1) and length (L) 5-30 times the internal diameter (d2) of the tube or without diameter change. Abrasive output speed can be varied by changing the diameter ratio (d2:d1) and/or tube length (L) and/or nozzle (24) distance (a) from the surface (3). Air flow is 150-400 cu m/h, preferably 230 cu m/h. Abrasive can be plastic particles, especially thermoset plastic particles, ash, fine particle clinker, corundum, quartz, metal particles, glass beads or mixture of these. The air supply hose line (20) is connected to the acceleration tube (21) and a tubular lance (22) which swivels through a 90 deg conical zone inside the cover (25). An abrasive metering device (18) connected to the mixture injector (19) is fed from a hopper (13) in a first container (11). Another container (10) on top of the first is fed with recycled air, dust and abrasive via a return line (28) and is connected to a vacuum unit (4). The cover walls (26) may be convex, concave or V-shaped or have joints to allow adaptation to different surfaces. Vacuum is produced at either a wet or dry vacuum unit, a pump, a compressor or a fan. Seals are located between the cover and the surface being treated.