Sugar dryer and VKT for ACS

BMA supplies plants for modernisation of Drayton sugar factory

Several years ago, the American Crystal Sugar Company (ACS) started to systematically modernise their Drayton, North Dakota factory. In 2019, it was the turn for a new BMA sugar dryer and a VKT vertical continuous pan for B product.

The drum dryer has a diameter of 3.2m and is 10m long. It is designed to dry 76t/h of sugar to a moisture content of 0.03%. The drum features a pre-cooling section, where the sugar is cooled to 55°C. It is then fed into an existing vertical sugar cooler. BMA also supplied the inlet screw conveyor, rotary airlocks, heat exchangers and a horizontal cyclone separator.

The 4-chamber VKT has a diameter of 4.8m and a total cylindrical height of 31m. It is designed to operate at a massecuite flow rate of 72.5t/h. If future needs call for a capacity increase, the VKT can be extended with a fifth chamber. This is a very economical solution. With the use of heating steam at only 0.7bara, the overall steam economy of the factory is considerably improved. The operating pressure of the VKT is at 0.2bara. Thanks to the VKT’s unique design, continuous operation is possible even if one of its chambers is in cleaning mode.
BMA also supplied the massecuite pumps and DynFAS microwave systems to measure the dry substance content in each chamber.

Project management responsibilities were handled by our local US project manager, with process and design engineering support from BMA experts in Germany.

Manufacturing of the drum dryer and the VKT was split between BMA’s workshops in Braunschweig and Greeley, Colorado. For the drum dryer, BMA Germany supplied the riding rings, trunnions and drum seals; BMA Greeley manufactured the entire drum, the inlet and outlet housing, and integrated the riding rings. For the VKT, our workshops in Germany supplied the calandrias, double conical bottoms and the agitators, while the vapour chambers, intermediate sections and bottom section were manufactured in Colorado.

The assembly and installation at the factory had to follow a strict sequence because the drum dryer and the VKT stand in close proximity to each other. The dryer is located in an existing building and the VKT in a new building attached to it, which had to be built at the same time. To make matters more difficult, the old drum dryer had to be removed from the existing building before the new one could be installed in its place. This, of course, could only be done after the campaign ended. And North Dakota campaigns are traditionally very long. The new dryer was slipped into the old building through the steel structure of the new building, where the VKT had not yet been installed. The VKT could then be assembled and the new building completed. Throughout the installation, BMA deployed its site supervisors on site.

BMA also provided commissioning support with our Germany and US-based process experts. The dryer started operation successfully with the beginning of the 2019/2020 campaign, at the end of August 2019. A little later, at the end of November 2019, the VKT was commissioned. By then, the factory had been running since the end of August. This is another benefit of building a VKT outside the sugar house wall without the need to first demolish the old pan station: this way the campaign can start at any time and the operators can then switch over to the VKT “on the fly”.