At Burns Energy Systems we have spent a considerable amount of time looking for ways to improve product yield from the French Process for manufacture of zinc oxide. Through extensive modeling we have identified the importance of achieving the ideal mixing of transport air and zinc vapour inside the combustion hoods.
We have found that eddy currents are generated by the powerful convection currents on top of the furnace and the crucible lids. When Zinc Oxide gets caught up in these eddy currents it can be diverted towards a stationary surface where it can drop out and collect. We have therefore designed the top of the furnace to be as streamlined as possible. We have made sure that the air being entrained at the hood is uniformly accelerated in the direction of the collection duct. Our unique crucible lid and combustion hood arrangement minimizes these zinc oxide losses.
The zinc vapour flame burns at about 2,300C. To make the environment around the furnace more comfortable for the furnace operator we have designed a radiation shield that works in conjunction with the rotating launder. The radiation shield features a woven wire mesh that is porous enough to allow the proper quantity of combustion air to enter the hood. The weave is overlapped to eliminate the radiation sight-line to the rest of the workspace. The shields are manually operated by the furnace operator using a simple lever and counter weight system
Grit from a number of sources can enter the system to contaminate the product. We have designed a grit catcher to collect 100% of all material >60 mesh while allowing 100% of the material <325 mesh to pass though. The Grit Catcher has an adjustable baffle which can be used to adjust the efficiency of the equipment and size of collected material. The Grit Catcher is usually installed in proximity to the furnace to be most effective.
In some cases a client may wish to source intermediate grades of zinc oxide materials in which case it may be better to consider the use of cyclones. These are usually installed as two cyclones in series, with the first cyclone operating as a grit catcher and the second cyclone collecting the intermediate grade of material. Cyclones usually operate at a higher pressure drop compared to the Grit Catcher and are therefore more expensive to run. We will be happy to advise and supply cyclones as required.