Monday 10th Aug, 2020

Yalumba winery converts to bulk bag discharging of granular tartaric acid

When the price of liquid tartaric acid doubled, one Australian winery made the switch to bulk bags instead with the help of Flexicon.

When the price of liquid tartaric acid doubled, one Australian winery made the switch to bulk bags instead with the help of Flexicon.

The modern wine business is highly competitive, requiring successful wineries to keep up with changing consumer preferences and respond to fluctuations in the market price of key ingredients.

Such was the case in 2018, when one of Australia’s oldest family-owned wineries, Yalumba Family Winemakers, learned that tartaric acid would double in price.

In response, it switched from purchasing tartaric acid as a liquid, to purchasing it in granular form supplied in one-tonne bulk bags. This would require the installation of a bulk bag discharger with integral flexible screw conveyor.

Switching from bulk liquid to bulk solids

Tartaric acid enables vintners to adjust and maintain the pH of grape juice as it turns into wine. At the correct pH, bacteria cease to grow, allowing the yeast to ferment the sugars while keeping the the wine fresh, lively and colorful.

“It’s a matter of getting that balance just right,” says Luke Wilson, Yalumba’s senior process engineer. But at twice the price, tartaric acid threatened to significantly impact the production budget.

Yalumba’s supplier of tartaric acid also offered a granular product in 15 kilogram bags, but manual dumping posed occupational health and safety concerns.

“It’s labour-intensive to mix into the wine,” Wilson says. “You’ve got an operator cutting open and emptying bags of 15 kilos. We purchase in the order of 100 tonnes of tartaric acid, and that makes a lot of bags to carry and mix by hand.”

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However, tartaric acid in granular form was less costly, especially when purchased in one-tonne bulk bags, prompting Wilson to research a bulk bag discharger to handle the material.

Among his prime concerns was the equipment manufacturer’s experience at handling tartaric acid, and the ability of the equipment to operate with minimal human intervention.

Speed of delivery was also paramount, as the equipment needed to be operational prior to the harvest of grapes. “We need it when we crush the grapes because we want to make all our pH adjustments early to give maximum protection to the wine,” Wilson explains.

Yalumba specified a Bulk-Out  bulk bag discharger with an integral flexible screw conveyor from Flexicon Corporation Australia. The system was delivered and installed within eight weeks of order confirmation, allowing the winery to mix tartaric acid granules with water prior to the grape-crushing phase.

Transferring contents of an entire bag to the mixing tank

The Flexicon BFF series discharger is equipped with a removable bag lifting frame used to forklift full bags from the plant floor into the discharger frame.

The flexible screw conveyor, Model 1450, transfers tartaric acid at a distance of three metres at a 48-degree incline at rates of 4.25 cubic metres per hour. All product-contact surfaces of the discharger and the conveyor are manufactured from 304 stainless steel, with the exception of the polymer conveyor tube.

A forklift positions the lifting frame above a full bulk bag on the plant floor, allowing an operator to connect four bag straps to corresponding Z-Clip bag strap holders. The frame with suspended bag is then forklifted onto spring-loaded Pop-Top bag extension devices atop the frame posts. A full bag compresses the springs, designed to progressively stretch the bag upwards as it lightens to compensate for elongation, promoting material flow through the bag spout.

To unload a bag, an operator pulls the bag spout into a hopper intake chute equipped with a side access door, sealing ring, and filter sock to contain dust. Untying the spout’s drawstring allows material to fill a 110-litre capacity floor hopper. Side wall angles are engineered to promote flow into the charging adapter of the flexible screw conveyor.

“From an operations point of view, loading the discharger is quite simple,” Wilson says.

“The steady feed of tartaric acid mixes quickly and easily in the 2000-litre tank aided by an agitator. 

At the conveyor’s inlet is a capacitive proximity level switch with a food-grade Teflon shield. It is connected via a touchscreen programmable logic controller to a delay-off evacuation timer. Once the conveyor is started, it runs until the bulk bag is empty, stopping automatically after the level of tartaric acid falls below the low-level switch, and the delay-off time period has elapsed. This ensures that the full contents of the bulk bag are loaded into the mixing tank to achieve the desired 50:50 ratio of tartaric acid and water.

The combined actions of the spring-loaded bag extension posts, and Flow-Flexer bag activators help achieve flow promotion. The activators raise and lower opposite bottom edges of the bag with increasingly longer strokes as the bag lightens. This raises the bag bottom into a steep ‘V’ shape free of dead spots.

The acid remains stable in the tank once it’s mixed with water. “It’s not going to fall out of solution or become microbially unstable,” Wilson says.

“Our business is making wine,” he adds. “We’re not experts in powder handling and because we were on a really tight timeframe, we relied on the expertise of the guys from Flexicon.