PLANTBatch

GLASS INTERNATIONAL SEPTEMBER/OCTOBER 1999 9

An efficient batch plant supplying high quality mixed raw materials is thekey to producing high quality glass from the furnace. Here D D Burgoon*

urges manufacturers to look to thebatch house as the starting point for

improving overall plant performance.

Today many glass manu-facturers are faced withthe need for greaterproduction capacity andthe need for greater

product quality to better competeand to improve the bottom line. As anew glass process line is designedand installed or as an existing fur-nace is rebuilt, not only is the focuson the furnace, but it is also on thebatch plant to help achieve theseprimary objectives.

TECO approaches a glass manu-facturing process as a chain and theprocess performance is only as goodas the weakest link in the chain.The best glass furnace, and/or fur-nace operation, cannot make qual-ity glass unless the furnace is fed bya batch plant that produces highquality mixed batch. Here some ofthe various batch plant processloops are discussed.

Raw materials handlingThe raw materials unloading systemis designed (or redesigned) to avoidcontamination from material tomaterial, as well as avoiding segrega-tion of respective raw materials.Another important consideration isminimising segregation of the mate-rials as the silos are filled.

Batch weighing systemsThe discharge of the respective rawmaterials from storage is critical andmass flow from each silo must beachieved either by proper silo bot-tom design, or by the use of mechan-ical flow enhancement devices. Eachweigh feeder is designed for bothcapacity and resolution, which is nec-essary to achieve desired statisticalweighing accuracy. For fine meshmaterials, with erratic flow character-istics, such as with E glass batch

materials, TECO hasdesigned and usesthe Superfine feederwhich regulatesmaterial flow anddelivers material tothe scale in minuteresolution for properweighing accuracy.

The scale system isthe heart of a batchplant. The capacityand resolution ofeach scale is designedto deliver desired sta-tistical performanceto suit each ingredi-ents weighingrequirements. Scale systems aredesigned and installed to preventinsidious weighing errors caused byinternal weigh hopper pressure, orpressure acting on the dischargegate or feeder.

Check scaleA check scale is an essential part ofevery TECO batch plant. Eventhough each raw material is checkedfor accuracy after weighing, it is pos-sible to obtain a batch error fromseveral sources, such as load cellfailure or operator intervention. Acheck scale may be redundant, but itis economical and provides assur-ance that an off recipe batch will notbe delivered to the furnace. Afterall, a check scale will more than payfor itself by catching just one offrecipe batch and thus preventinglost production.

The check scale can be installedbefore or after the mixer or pneu-matic blender/transporter, or, in aneffort to conserve space and cost,the mixer or blender/transportercan be mounted on load cells to actas a check scale. Todays scale

instrumentation incorporates elec-tronic digital filtering to provide astable scale even on an operatingpiece of equipment.

Mixed batch handlingHomogeneity of mixed batch deliv-ered to the furnace is also an areathat has improved significantly inrecent times. Modern day furnacebins have both input and outputprovisions for mass flow, whichassures unsegregated delivery ofbatch to the furnace doghouse.

Cullet returnAutomatic return of both hot andcold cullet is a basic part ofvirtually all glass plants today,primarily to eliminate manualhandling and the associated safetyhazards. Maintenance free time isimportant in cullet handling andhigh wear resistant materials cur-rently available prolong the needfor maintenance.

Better plant performancebegins at the batch house

* D D Burgoon, director of batch plant projectsToledo Engineering Co Inc, Toledo, Ohio, USA.Fax +1 419 537 1369.

The head house floor of a batch plant designed and built by TECO.