Storage and Processing Aspects of Frozen Beets David L. Cummings, Don Badt, Larry Riggs, Russ Fullmer and Richard S. Parrill Holly Sugar Corporation

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1 Storage and Processing Aspects of Frozen Beets David L. Cummings, Don Badt, Larry Riggs, Russ Fullmer and Richard S. Parrill Holly Sugar Corporation East Holly Street Sidney, Montana

2 Introduction As the economics of recent years in the sugar industry has favored those plants capable of extending the length of their campaigns, the necessity of developing methods to improve long term storage of beets has become increasingly important. While no storage method will improve the technological value of a beet when compared to a fresh beet, it must significantly reduce the loss of value of the beet to be feasib[e. With this in mind, Holly Sugar's Sidney factory was given the opportunity to evaluate the feasibility ofintentionally freezing beets for the purpose of extending campaign past the typical end of March 1. Two phases of investigation were entered into. The initial evaluation was performed during the campaign, with the intention of evaluating the factory's capability to handle frozen beets. A scaled up second phase was begun during the campaign, with improved storage techniques and a more in-depth evaluation of the technological value of beets kept in long-term storage by freezing. Although the slicing of beets placed in long term storage will not commence until the first week of March 1997, some qualitative conclusions have already been drawn. Phase 1: Campaign Harvest for the Campaign began on September 13, and lasted through October 26. A total of 773,429 net tons of beets were received, of which a modest 20,000 tons were prepared as a test pile for long term storage by freezing. Several criteria were used to select the beets for long term storage. Relatively clean, dry beets from contracts with low tare and high sugars were segregated into the designated 20,000 ton portion of a complete pile for freezing. A control pile was prepared using similar criteria, and treated as a typical ventilated pile for long term storage. The initial quality of each of the two piles can be seen in Table 1. Compared to the overall harvest sugar of 17.70%, the control pile averaged 0. 12% lower sugar while the test pile was 0.3 5% lower in initial sugar. The control pile was found to have beets of higher in purity that the harvest average, while the purity of the test pile was comparable to that ofthe average for the harvest. T a bl e 1. I mtl.. al Qu a r lty 0 fcontro andfrozen P'l 1 es, C ampmgn. Pile Type Harvested %Sugar Beet Purity Harvest Average Control (Normal Ventilation) Long-Term Storage (Frozen Pile)

3 Each of the two piles were then subjected to normal ventilation practices for Sidney through the remainder ofoctober and November. Table 2 compares the cooling procedures used on each ofthe two piles. Typical ventilation practice in October and November was rapid cooling of the pile to approximately 30 F, and subsequent holding ofthe pile at that temperature. The control pile was also processed at this time, resulting in minimal losses and good operating conditions. T a ble 2 C00rmg Practlces fior Frozen and Con t ro I P I Ie. Control Pile (Normal Ventilation) Long-Term Pile (Frozen) Initial Cooling of Pile (October, November) Fans on until 30 F. Fans on until 30 F. Secondary Cooling (December) Vent holes blocked no further cooling. Fans on with daily median temp < 10 F. Final Storage Temperature Approximately 30 F. I I Average Temperature 11 F. On December 6, with an average ambient Figure 1. Relative Temp<nIUre oflong T<mI Stcragc Pile. temperature of 7 F and a forecast for an extended period of similar temperatures, Nonnal VCIIlti.lalioa ventilation fans were again turned on by ll'!... Larry Riggs. Constant monitoring of pile temperatures by Riggs showed continued rapid cooling for a few days to approximately 22 F, where the pile temperature stabilized Time, 10 daj.. -+ for several more days. The phase change was complete by December 23, allowing the pile to reach its target temperature of 11 F by December 26, when the fans were shut off (Figure 1). During this time, no further cooling of the control pile was performed other than passive cooling by ambient temperatures. On the morning ofdecember 28, the frozen pile was opened, and preparations were begun to bring slice to the factory completely on frozen beets. Two yard long, six inch thick spikes of plate steel were bolted to the bucket of a backhoe proved to be adequate to the task of breaking up the pile. At 8:00 am December 29, one hundred percent of factory slice began coming from the frozen pile. Loads of frozen beets were delivered to the wethopper, where the flumers were ready to receive them. The process of fluming a beet rapidly became one of trial and error. It was soon discovered that dumping an entire load of beets into the wethopper at a time, the normal practice for unfrozen beets, produced a solid mass of frozen beets, which then had to be poked and prodded out of the wethopper. Dumping smaller amounts of beets out of the trailer at a time soon became the standard, 101

4 allowing the flume to better able keep up with the incoming beets and preventi ng a large, rapid freeze from occurring. The flume water temperature was 10 C, and did not significantly change over the days of processing frozen beets, presumably due to the large volume of water compared to the relatively small amount of beets in the flume at any given time. The beets arrived at the slicing station with nearly all of the outer layer of root tissue having been removed, having been lost in the flume and beet washing area. A large increase in the percent sugar in flume water was also observed, presumably to the skin lost from the beets. For the most palt, the slicers did not have too much trouble with the frozen beets, although some minor problems developed and were overcome. The cossettes produced appeared to be of a workable type through an RT diffuser. No major flow troubles developed in the diffu ser while processing the frozen beets. Transfer through the RT diffuser was adequate with a slice rate of approximately 200 tons per hour. When a rate of21 5 TPH was attempted, diffuser plugging at the discharge screens was seen to occur by observation of inferior juice flow. Increased heat was found to be needed in the diffuser. Two raw juice recirculation pumps were in service, to allow for adequate heater temperatures. Steam vapor changes were made in the raw juice recirculation heaters to compensate for dropping temperatures throughout the beet end. Although the temperatures remained low after all changes were made, the carbonation and fil tration processes continued to operate in a acceptable manner. Perhaps the greatest loss of slice time occurred during the changing of the beet knives. Beets in the knife hoppers tended to freeze into a solid mass during the fifteen to twenty minutes required to change knives. An additional ten to twenty minutes was spent poking, prodding and water flushing out the frozen bridge of beets above the slicer. The frozen beet slice was ended January 2nd, 1996, leaving approximately 3,000 tons of the frozen portion of the pile unsliced. Ventilation fans were again used to drop the temperature of the remaining beets even further. These beets were saved until February 12 u " when they were sliced as the final beets of the campaign. A return to these beets saw a remarkable rise in cossette sugars, raw juice purity and thin juice purity over those beets sliced in the previous days which had been stored as a "typical" ventilated pile, vividly demonstrating the benefits of freezing beets for longterm storage. No significant difference in process materials usage was found between beets from the control pile (typical) beets and the frozen beets, with the exception of kiln operations (Table 3). Slightly more limerock was required per ton offrozen beet than for the typical beet. The precise cause of this was not known., although it may have been due to a slightly slower slice per hour on frozen beets with no corresponding reduction in kiln operations. Energy usage was higher in the factory on frozen beets, but not significantly different in the pulp driers. Losses were similarly impacted, primarily in lime flume loss. This may have also been the result of disproportionate kiln operations. 102

5 . Table 3 M aten'al andenergy usage, T yplca I vs. Frozen Beets Net Tons Net Tons % on Beets % on Beets Material Usages Typical Frozen Typical Frozen and Losses Beets Beets Beets Beets Tons Beets Sliced ,00 100,00 Tons NonSugars: Diff Juice 600, ,16 2,09 Tons NonSugars: Thin Juice la2 I 1.53 Tons Lime , A2 Tons Rock to Kiln 1,063, , Draft , Carbonation Elimination 34, Factory MTherms 318, lao Drier MTherms 110, OAO OA3 Tons Sugar to Lime Flume ,86 0,05 0,10 Tons Sugar to P uln T.oss o 1R The quality of sliced frozen beet versus the typical beet was found to be nearly identical, with a few exceptions (Table 4). Slightly lower pressed pulp moistures were found in pulp from the frozen beets, presumably due to better utilization of presses, Higher colors were observed in thin and thick juice, as well as standard liquor. While these results suggest some loss in overau beet quality, no definitive conclusions can be drawn due to the disparity between processing times and the slightly lower initial cossette sugar in the beets frozen Yield was not compared, as a combination of fresh juice and thick juice from storage was taken to the pan floor, with the remaining fresh juice going to storage, This practice prevented meaningful conclusions about sugar end operations from being made, Table 4, Anal ical Results, T Cossette Sugar Diff, Juice Purity Thin Juice Purity Target Thin Juice Purity Pulp %Moisture Lime Salts Thin Juice Color Thick Juice Color ical vs, Frozen Beets, Typical Beets Frozen Beets (Mid November) (Early January) 16.61% 16.65% 88.37% 88,32% 92.00% 9l.44% 92Al% 92A8% 73.90% 72,34% 0,02% 0,03%

6 Phase Two: Campaign The second phase offrozen beet evaluation was initiated with the beginning of harvest on September 12, 1996 with the intent ofconstructing a much larger pile of beets frozen for long term storage, and then holding them until the end of campaign for processing. No control pile was developed, as it was determined that comparisons of frozen beets would be made to normally ventilated beets processed just prior to those frozen. Quantitative data was not available at the time this paper was written, due to unexpected late addition of 50,000 tons of unfrozen beets from Moses Lake, Washington to the Sidney inventory. Improvements made to the preservation techniques for the long term pile included levelling of the top ofthe pile to minimize the formation of hot spots, and the covering of the pile with a protective tarp. As 60,000 ofthe approximately 840,000 tons of beets harvested were earmarked for freezing, these changes in procedure were significant. Once again, only beets that were relatively clean and dry with low tare were allowed into the frozen pile. Qualitative evaluations of this pile have been encouraging to this point. The initial cooling of the beets in the pile to be frozen was performed as usual. The window of opportunity fo r freezing the pile began on December 14, with the fans being shut off on December 28. The required two weeks to freeze the pile was a week shorter than the previous year, likely due to a much colder air mass with which to work. The average pile temperature was found to be ODF after the fans were off. The tops of the piles were then levelled with a snowcat, and cleared of some of the accumulated snowfall. Additionally, a portion of the north end of the pile was removed to eliminate concerns of hot spots in this poorly ventilated section. A white reflective tarp was brought in for installation. In approximately five hours time, four tarps had been dragged in place, sealed together and suctioned down over the pile by reversing the fans. As previously mentioned, the late addition of fifty thousand tons of beets from Moses Lake delayed processing ofthese beets until now. The long-term storage of these beets enabled Sidney to pick up the additional load with a significantly lowered risk of losing beets. Under the unusually warm storage conditions experienced in Sidney through the last two weeks offebruary, normal ventilation practices could have resulted in significantly higher pile losses, or total loss of beets altogether in either Moses Lake or Sidney. Conclusions and Future Considerations In light ofthe current mind set in the United States beet industry ofmore tons, lower cost and longer campaigns, the need to improve storage of beets becomes significant when investigating ways to increase production. The positive implications of improved long term storage for beets in Montana are beneficial to the long-range outlook of sugar production at Sidney for many reasons, such as: 104

7 Long term pile storage of beets in Sidney preserves the technological value of the beet significantly better than traditional pjle storage techniques. Improved ability to handle, slice and process frozen beets provides potentially greater opportunity for increased sugar production at Sidney. Enthusiastic grower support makes expansion and improvement plans appear feasible and realistic for the Sidney factory. Long term storage utilizing frozen beets likely will be used increasingly in the years to come in Sidney. 105