Normal arrangement for raw materials process weighing, batching and mixing

This page describes a normal arrangement for raw materials process weighing, conveying, batching and mixing technology.

Raw materials workshop is responsible to provide qualified batch (with accurate chemical compositions and good uniformity) to the furnace, providing fundamental condition for production of high quality glass.

Viewing from layout, the batching system of the raw materials workshop can be divided into two schemes, i.e. row arrangement and tower arrangement. The tower arrangement has advantages of less occupied area, compact arrangement, short flow sheet, which is benefit for concentrated management; on the other hand, it has high requirements to the performance of the equipment and management level, and the arrangement inside the workshop is complicated. Weighing-in is the main weighing technology, which may result in internal error easily. The row arrangement has advantages of flexible arrangement, smooth process. Weighing-out method can be adopted to ensure weighting precision. However, it has long flow sheet and more production links. We can provide different arrangement schemes upon the request of the Owner.

If the silica sand is transported into the factory in the means of waterway, they will be first discharged into the receiving hopper via the fixed type wharf crane equipped at the special wharf of the factory, then, through belt conveyor, conveyed into the homogenization hall or silo for storage. If the silica sand is transported into the factory by means of truck, they will be first discharged into the sand pit, and then conveyed to the homogenization hall, or to the silo via grabber. The storage amount of the crane silo or homogenization hall will be determined by the daily melting capacity of the furnace. In order to reduce the fluctuation of the silica sand compositions, silica sand homogenization hall is built. The silica sand from crane silo is conveyed to the distributing belt of the homogenization hall via belt conveyor and bucket elevator. The discharging trolley is stacking the materials uniformly in thin layer. Reclaimer is adopted to take the materials from the section uniformly. Then, they are sent to the silica sand silo via belt conveyor and bucket elevator.

If being transported into the factory by truck in lump, dolomite and limestone will be discharged into receiving pit, and then be conveyed to the lump silo via bridge type grabber. During production, bridge type grabber will take the lump material to the intermediate hopper, and then fed into the jaw crusher for crushing. Two-stage or three-stage crushing process will be adopted. Jaw crushing is adopted for primary crushing and hammer crusher is adopted for fine grinding. Generally, one crushing system is installed for limestone and two crushing systems are installed for dolomite. After fine grinding, the materials will be lifted to hexagonal screen for sieving. Powder with qualified grain size will be conveyed to respective powder silo via bucket elevator and belt conveyor. Those materials above the screen will be conveyed back to the hammer crusher for re-grinding.

Soda ash, salt cake and feldspar are transported into the factory in qualified powder and stored in powder storage shed, unpacked and dumped manually and lifted to the hexagonal screen (plane shaking screen for feldspar) via bucket elevator. Qualified powder will be conveyed to respective powder silo via bucket elevator and belt conveyor, while those above the screen will be conveyed back to the cage mill for regrinding. Small amount of feldspar above the screen will be removed by trolley.

Bagged coal powder and other small materials will be lifted up to the top of the powder silo via electric hoist and dumped into the silo manually.

Interrupted scale is adopted. Amount of each batch shall match the capacity of the mixer. In which, silica sand, dolomite, soda ash, limestone and feldspar adopted weighing-out scale, while salt cake and coal powder adopted weighing-in scale. Vibrating bin is installed under the batching hopper to avoid blockage or formation of “funnel flow”. In this way, the feeding of material can be smooth and uniform. After accurate weighing, they will be discharged onto the weighting belt. Salt cake and coal powder will be discharged into the pre-mixer first, and then fed onto the weighing belt through vibrating feeder. Weighting belt will convey the accurate weighed materials to the mixer for mixing.

Imported or local mixer can be adopted for mixing system.

Uniformly mixed materials, together with the cullet, will be conveyed to the charging hopper of the furnace via batch belt conveyor.

In order to prepare high quality batch with accurate chemical compositions and good uniformity, the chemical compositions, grain size, water content of the raw materials coming into the factory, as well as their fluctuation range shall be strictly controlled, and the weighing accuracy and mixing uniformity shall be increased to improve the glass quality and extend the furnace life. Following measures can be adopted:

• 5.1 High purity and stable quality silica sand (with grain size meet the requirements) and other main raw materials shall be adopted;
• 5.2 In order to reduce the fluctuation of the silica sand in the course of transportation and storage, or due to difference of the mining places, ensure stability of silica sand compositions, water content and grain size, silica sand homogenization hall is built. The silica sand is distributed by the stacker uniformly and taken by the reclaimer from the section.
• 5.3 On-line water content inspector is installed for the silica sand weighing system, timely measure the water content of the silica sand, feedback the result to the weighing control room, for compensation of the batching amount.
• 5.4 High precision, good stability, high reliability, complete function and convenient electronic weighing and batching control system are selected. Row arrangement is adopted. The batching system has functions like fast and slow feeding control, over-tolerance, over-time upper limit and lower limit alarm, automatic tare removing, over-rush, etc. In addition, it has functions of formula setting, formula calculation, production parameters display, table making and printing, etc.
• 5.5 Imported mixer is adopted to ensure the uniformity of the batch.
• 5.6 Electromagnetic iron separator is installed before charging hopper of the furnace, to avoid in-take of the mechanical iron occurred during production process.

7. Components of batch
7.1 Raw materials for low iron super-white glass

In addition, a quality batching controller is enable the batching equipments work more safely and efficiently.