Bulk bag fillers key to success of massive sulphur recycling project

Paul Boughton
Sulphur is a by-product of diesel fuel that's applied to the land as a fertiliser amongst its many other uses. Until recently, the market value of sulphur had remained depressed for one the longest periods ever. This made the cost of recovery uneconomic so it was just stockpiled as a result. However, when the price increased five-fold, recovery became a profit opportunity for the owners of an oil refinery in Kenai, Alaska, USA.

They contacted AIMM Technologies, a Texas-based oil industry service-company with 15 years recycling/processing experience and long track record on the North Slope of Alaska.

"Alaska is a logistical nightmare in which to recycle petroleum by-products such as sulphur," confirms Brooks Bradford, president of AIMM Technologies. "Sulphur is a hazardous material that can easily catch fire. For this contract, we had to bag the sulphur, move it to a storage site, move it from the storage site by truck to a port and then load it onto an ocean vessel for delivery to market. When we got the go ahead to recover the sulphur, we concluded that the best way was to use bulk bags. For this, we needed a means of filling them. One specific requirement was that the bagging facility had to be easy to dismantle for use at another sulphur recovery site once recovery at this site was complete."

"After researching various suppliers, we selected Spiroflow Systems, which was able to meet our tight delivery requirement of four weeks - with installation and start-up taking no longer than an additional two weeks, a very tight schedule," Bradford added. "Spiroflow was the only supplier who could meet our tight deadline."

Spiroflow supplied two of its Spirofil Model C1-2 weigh fillers which are specially designed for pallet loaded bulk bags/flexible intermediate bulk containers (FIBCs). The Model C1-2 is ideal for FIBCs of 900-1800 kg capacity that are removed from the filler on a pallet when full. Model C1-2 Fillers incorporate an approved weigh platform and those supplied to AIMM were complete with integral powered rollers for fast and easy removal of filled bags. The FIBCs at Kenai each held 1500kg of material, were a metre in diameter and custom made of conductive polyester for the safe handling of sulphur. Once filled, the FIBCs were powered off the fillers onto gravity roller accumulating conveyors where they awaited removal by forklift truck.

The two bulk bag fillers were customised before dispatch from Spiroflow's Monroe plant in North Carolina. The power supply, for example, had to be modified to a higher standard since an electric spark could ignite the sulphur.

Once manufactured, the two bulk bag fillers were assembled onto a skid and delivered by truck to the Kenai, Alaska site. It took the truck five days to complete the journey. The company also sent a commissioning engineer to the site for two weeks to supervise installation, commission the filler and to train the operatives. "We appreciated the extra effort by Spiroflow since we were not familiar with bulk bag fillers," Bradford noted. "So, we needed training too."

The bulk bag filler facility at the Kenai petroleum refinery comprised a nine metre high frame to support a feed hopper, the two Spiroflow Model C1-2 bulk bag fillers and two roller accumulating conveyors. Full 1500kg capacity bags were driven off the fillers onto the gravity roller conveyors. Using stevedore straps, forklift trucks picked up the bags to take them to the storage yard or to load them directly onto trucks for delivery to the dockside in the port of Homer, several hours' drive away.

AIMM Technologies designed the nine metre high support frame and the hopper into which the sulphur from the sulphur stock yard was loaded (Fig. 1), while Spiroflow was responsible for customising two of its own bulk bag fillers and designing a square 'trouser leg' chute system that attached to the bottom of the feed hopper. Control of the sulphur from the feed hopper down either of the trouser-leg chutes and into the bulk bag fillers was by way of a series of diverter valves and slide gate valves (Fig. 2).

Sulphur was loaded into the bulk bag fillers' feed hopper by bucket loader from the storage pile on the refinery site. The sulphur was dumped on a conveyor belt by a bucket loader and moved at up a 10metre incline into the top of the hopper. Since the sulphur has extraordinary binding properties and weighed 57kg/ft3, it had to be funnelled, not poured, into the hopper to assure easy discharge into the trouser leg chute. From the hopper, the material was directed through the diverters to the bulk bag fillers. The remote mounted controllers, supplied by Spiroflow, opened and closed the gate valves according to the weight of the bags. When the bags where close to their target weight, the controller shut-down the flow rate through the gate valves, allowing only a trickle flow into the bag until it reached its 1500kg capacity.

The FIBCs had straps that attached onto the fillers' bag support hooks one at each corner. These automatic, quick release latching hooks released the straps when signalled to do so by the controller thus allowing the pallet mounted bags to be driven off the fillers by the powered rollers onto the queuing conveyors.

According to Jeff Deese, vice president of the Alaska Division for AIMM Technologies, the facility was in operation for 14 weeks with 10 people working each eight-hour shift, four of whom were at the bagging station.

The facility averaged 300 bags a shift, reaching a high of 404 bags on one of the shifts. Three hundred bags a shift is an average of 18.75 bags per hour per filling machine. In all, 36 000t of sulphur was recovered in 27 000 FIBCs.

Bags were taken from the storage facility in one of four trucks that moved bags continuously to the Port of Homer, Alaska, about three hours from Kenai. The sulphur was sold at Homer to a third party who shipped it to an inland river port in China where it will be used mainly as fertiliser (Fig. 3).

The bulk bag filling facility was recently dismantled and is in the process of being reassembled at another sulphur recovery site in Canada where it was converted to handle 1800kg bags instead of the 1500kg bags handled at the Kenai facility, an increase in capacity of 21 per cent

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