Objective
The aim of the project is to demonstrate that substantial energy savings can be achieved by the installation of an air flotation oven for drying and curing the coatings on metal strip. In particular, the aim is to show the flotation of steel strip from a continuous coil, with wet coatings applied by means of air pads, through the initial drying stage without causing any disturbance to the high quality of finish required.
An oven consisting of three heating zones each 6 meters long (equipped with air bar technology) and installed in a continuous coil coating line.
The oven successfully "floated" steel and aluminium up to 1.6 mm thick on a continuous basis, without causing any disturbance to the wet coating, maintaining the high quality of finish required.
After 2 months of operation a major problem was highlighted. A build up of combustion products in the plates of the recuperator caused a reduction of exhaust volumes. A full appraisal of the problem was completed, and after investigation into cleaning methods and replacement units within the recuperator, it was confirmed that the heat recovery system could not be made to operate satisfactory and safely. Therefore this part of the system was disconnected.
It was decided to continue on the basis of monitoring the energy saving from the flotation technique only; hence the original energy saving objective was not attained due to the problems encountered with the heat recovery recuperator.
The most economical means of coating sheet metal is by treating it in its base form of flat coiled strip. A coil coating line normally incorporates a catenary oven to dry and cure the finish coatings. In catenary ovens the air distribution plenums and nozzles are at least 400 mm from the product. With the air flotation principle this is reduced to 75 mm. The air cushion created enables the strip to float but, more importantly, the heat transfer rate is considerably increased. A heat recovery recuperator will be installed in the exhaust of the oven to pre-heat the incoming ventilation air.
The oven contains three independent heating zones, each 6 m long, where solvent removal and strip heating occurs. This system of three zones allows flexibility of control in terms of air velocity and temperature. The material is supported throughout the oven by specially designed airfloat nozzles above and below the strip. The heat input to each oven zone is provided by a gas burner which is positioned on the suction side of an air circulation fan. The temperature in each zone is sensed by a thermocouple linked to a temperature controller which regulates the gas flow to the burner.
The installation will be continuously monitored over a period of one year for fuel and electricity consumption, ventilation rate and line speed. A careful log will also be kept of the quality and thickness of the applied coatings.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
WS5 4AX West
United Kingdom