Expansion and modernization of Renville sugar factory

Southern Minnesota Beet Sugar Coop's factory at Renville, Minnesota, USA, was built in the mid-seventies for a daily slice rate of 6,000 sht (5,400 mt) and presently processes approx. 9,000 sht (8,200 mt) per day. A bold reconstruction and modernization program now is aimed at increasing the slice rate to 16,000 sht/d (14,500 mt/d). All the work involved will be accomplished stepwise due to the short time available between the rather long campaigns.

For the 1998 campaign, BMA integrated four white sugar batch centrifugals of type G 2100 into the existing sugar house of the Renville factory. Due to extremely short lead times, the machines had to be completely shop-assembled for airshipment to the USA. At present, the four centrifugals process an average of 1,300 sht (1,200 mt) of white sugar per day.

For the main reconstruction phase at Renville, the following stations were expanded and/or newly set up for the 1999 campaign:

	Beet receiving
	Beet preparation
	Slicing
	Extraction
	Pulp pressing
	Pulp drying
	Waste water treatment

In this connection, BMA was awarded an order to plan, supply and supervise assembly and erection of the following equipment:

	1 Countercurrent cossette mixer for 16,000 sht/d (14,500 mt/d), 8.2 m dia. x 10 m
	2 Extraction towers for 8,000 sht/d (7,250 mt/d) each, 8.6 m dia. x 21.61 m extraction length
	1 Defoamer
	4 Cossette pumps
	4 Vertical pulp presses HP 4000 M

The countercurrent cossette mixer is the biggest unit ever built in the world. Downstream of this advanced cossette mixer, two proven and reliable BMA extraction towers are provided.

For lack of space, the two extraction towers had to be set up outside the old main building. In view of the extreme weather conditions prevailing during the long campaigns (180 to 220 days on an average, the customer wanted the complete extraction plants and pulp presses to be set up in an extremely compact way without the requirement of any additional outdoor conveying equipment.

Two vertical pulp presses each are directly associated with the extraction towers; there are no intermediate conveying elements such as screw conveyors or belt conveyors. An adjustable level-controlled flap distributes the pulp coming from the two conically arranged discharge screws of the extraction tower to the two pulp presses (sketch, photo).

The pulp presses employed are of the proven HP 4000 M type. For further details of this press, refer to page 14 of BMA Information 35/1997. The pressed pulp from the four pulp presses are fed directly, i.e. without an intermediate pressed pulp hopper, to two evaporation pulp dryers.

As the factory cannot achieve its final beet slice rate in the current 1999/2000 campaign, a pressing aid station was not installed yet. Nevertheless, an appropriately lower spindle speed allowed high dry substance contents in the pressed pulp even at the present slice rates.

Though assembly and erection of the equipment could not commence before the end of the campaign in March 1999, the factory with its new stations already resumed campaign operation in early September. The whole project was under extreme pressure of time, and therefore some of the usual test runs of the individual stations were dispensed with.

In spite of all these complications and inevitable, though quickly overcome, initial problems with the new stations, operation stabilized very soon.

Now the plants designed by BMA are operating, both technically and technologically, to the customer's full satisfaction.

Currently, the extraction plant and the pressing station operate at the following parameters:

After completion of the other planned factory expansion phases and an enlargement of the beet growing area to more than 140,000 acres (57,000 ha), the Renville plant of Southern Minnesota Beet Sugar Coop. will be the biggest beet sugar factory in the USA and, due to its long campaigns, the biggest beet sugar producer in the world.