The choice of the batch transport depends essentially on the flow properties and the humidity of the batch. The transport by means of screw feeders is advantageous for humid and hardly flowing batch susceptible to produce caking. For all other batch types, transport by means of vibratory chutes is also possible. Dry and preheated batch from a batch preheater should be conveyed by means of screw feeders, as the volumetric flow can be better controlled by means of screw feeders due to the flow properties of this kind of batch.
There are several running systems on furnaces melting up to 80% cullet. The screws themselves have a hardened coating to maximise service life and in several innovation steps the design was perfected to what it is today. Current screw life in normal operation is estimated to be about 1 year and the experience indicates that this is a realistic figure.
The charger has already shown its ability to handle cullet grain sizes typically used by manufacturers of high quality glassware. The machine can also cope with single larger pieces of cullet, such as container necks and bottoms, that can sometimes be found in the batch.
In many cases it is possible to replace an existing charger with an EME-NEND ® machine. However, there are many designs and sizes of doghouse in existence and so it is necessary to check each case individually. The first customer has installed EME-NEND ® machines on all his four regenerative furnaces within one year of the initial installation. On three of the furnaces existing conventional pusher machines were replaced by EME-NEND ® units on the run
The maximum throughput of the charger depends on the cullet content. After the latest revision of the design the largest model built so far (EME-NEND® S3) can handle up to 480 tons per day. Thus it is possible to run the furnace with a high melting capacity with just one dog house and batch charger – a clear saving in capital investment.
The pusher arm is the only piece which is water cooled, but the screw feeders and the discharge pipes do not need water cooling. The quantity of required cooling water is low and the risk that water can penetrate into the Doghouse is considerably reduced.
If two chargers of the modular system are used, it is possible to remove one charger from the Doghouse and to carry out maintenance and repair works while the other charger is fully functioning. This means that the charging system is partially redundant. If the chargers are dimensioned in such a way that already one charger can handle the total furnace capacity, this means that the chargers are fully redundant. In this case, it could be possible to use only one Doghouse instead of two Doghouses which results in considerable investment savings.