Loading and Distribution
Botswana Ash (Pty) Ltd has two loading facilities; one for soda ash and one for salt where products are dispatched in either bags or bulk through transportation by rail and road.
Coarse salt is despatched as bulk or bagged product.
The bulk wagons are loaded by a pay-loader. Each wagon is weighed on a weighbridge to determine the mass of salt that is being despatched. Typically, a bulk wagon will contain 48 tonnes of salt. Chemical grade coarse salt is the main bulk product.
The salt is reclaimed from the applicable stockpile by pay-loader. The pay-loader feeds a hopper which has a screw discharge. The screw meters the flow of salt into the bagging plant. The current rate is 20 t/h. The salt then goes to a bagging silo which has a capacity of 50 tonnes. To prevent the salt from caking in the buffer silo, 10 ppm sodium ferrocyanide is added to the salt before the silo.
To comply with health regulations in the various countries of distribution, potassium iodate is added in powder form before the salt goes to the bagging silo. The target iodation is 65 ppm, measured as iodine, but the addition can be varied depending on requirements.
The bagging line consists of two metering screws which discharge 50 kg ± 0.5 kg into a hopper. The hopper will discharge its weighed contents into a bag as soon as one has been positioned by the operator. While one hopper is discharging, the second is being loaded by its screw, thereby increasing the overall bagging rate to typically 15 t/h. The bags are stitched closed and conveyed to the rail wagon or road truck for loading.
Bagged 50 kg coarse and fine salt can also be loaded onto road transport to supply our regional markets.
Fine salt is only sold in 50kg bags. The bagging plant is fed from the milled salt silos via star feeders, which regulate the flow of salt out of the silos. The feed rate is 120 t/h. As with the coarse salt, potassium iodide is added, when required, before the fine salt goes to the baging silo.
The 50 kg bagging line is identical to the bagging coarse salt line. Bagged 50 kg coarse and fine salt can also be loaded onto road transport to supply our regional markets.
Dense ash is reclaimed from the soda ash warehouse and transferred to a 280 tonnes hopper. Bulk wagons, 1 tonne bags and 50 kg bags can be loaded from this hopper.
Bulk (BSA) wagons were specifically designed and built for Botash by Botswana Railways (BR). FKMJ wagons that are supplied by TFR are also used for bulk loading of soda ash. Both types of Wagons are top loading and bottom discharge wagons. The wagon to be loaded is positioned under the hopper on a weighbridge. The hopper is fitted with four telescopic loading chutes which are lowered into the wagon, forming a dust tight seal.
The loading operation is started by opening four rotary valves fully. When 40 tonnes of soda ash has been loaded, the valves shut down to a dribble feed which is approximately 20% of full flow. The loading operator stops the loading when the wagon has a net mass of approximately 48 tonnes. A loading rate of 150 t/h is typically obtained.
Both 50 kg bags and 1 tonne bags can be bagged from the soda ash loading hopper. The 50 kg bagging system is similar to that used for the bagging of 50 kg salt, except there is no metering screw. Instead, a conveyor belt is used to feed the loading bin, which is on load cells. The 1 tonne bags are filled using a conveyor belt with a flexible discharge chute which fits into the loading spout on the bag. Once loaded, the spout is tied closed and the bag transported to a rail wagon for loading. Both lines operate at approximately 10 t/h.
Light Soda Ash
Light soda ash from the compaction plant is bagged into 50 kg bags using a bagging system similar to that used for salt bagging.
The bagging hopper has a capacity of 50 tonnes, while the bagging rate is 10 t/h. Bagged 1 tonne and 50 kg soda ash bags are also loaded onto road trucks to supply the regional markets of Botswana, DRC, Malawi, Zambia and Zimbabwe.