Du Toitskloof steps into the future with new chiller plant

By Ilana Koegelenberg

The famous Du Toitskloof wine cellar has been around since 1962, but as the operation grew over the years, so did its cooling need, necessitating a staged chiller plant upgrade.

COVER

At the entrance to the Du Toitskloof Pass near Rawsonville, the Du Toitskloof co-operative wine cellar began production in 1962 under the management of Ursus Schirmer. He was succeeded by Ernst Gouws, then Philip Jordaan, and currently Shawn Thomson, the overall production manager.

Du Toitskloof boasts 22 member farms that belong to 11 families, most of whose forebears counted among the founding members of the cellar. They all live in a close-knit community within a radius of 10km from the cellar and all take a close interest in its activities. Between these members, they harvest about 900ha of grapes every year.

Initially, the cellar only consisted of a single steel-framed warehouse structure, which was later duplicated, doubling the cellar’s production and storage area. Additional offices and tasting rooms were built in the early 1990s, to accommodate expanding tourism activity and administrative needs.

In 1962, their first intake was only 6 000 tonnes of mostly Hanepoot grapes. Now they process about 25 different cultivars. Currently, the cellar tries to process about 16 000 tonnes of grapes annually and as such, has to purchase about 1 000 tonnes from outside farms as well. With their current set-up they can process an impressive 500 tonnes of grapes a day.

Du Toitskloof currently produces 40% bottled wine and 60% bulk wine. The aim is 50–50 eventually. They have grown quite a lot in the past three years from about only 26% bottled initially.

Every year, of their own harvest, they produce between 12 and 13 million litres of wine. Then they also purchase round about another five million litres annually. They are working towards 25 million litres eventually, with a breakdown of 60% white wine and 40% red wine.

DPS intro

A LONG HISTORY

Philip Jordaan, the previous winemaker, knew Steven Palvi Snr from his APV Hall Thermotank days, where Palvi Snr was the winery manager. Palvi Snr got involved at Du Toitskloof in 1978 when the new plant room was built with a Dunham-Bush compressor (110kWr), which had been moved there from the old plant room. Over the years, APV also added a Carrier5H86 (280kWr) and a Trane 3E80 (280kWr) machine, both of which were removed in January 2017 to make place for the new Aermec machines.

In 1991, Palvi Snr started Wynroete Verkoeling, a contracting company servicing specifically the local wineries, taking on DuToitskloof as one of his first clients. Wynroete initially started with 15 wineries and now services 150 wine cellars that stretch as far as Upington.

Wynroete’s first project with the Aermec team was during the upgrading of the Ladysmith cellar in 2014; since then they have installed about 4MW of Aermec chillers in the wine and mushroom industries. This is set to increase as the current phase down of R22 refrigerant drives the upgrading of more and more plant rooms.

Port barrels. An old 1980 open-drive reciprocating Trane 3E80 compressor that was in the plant room before. First Aermec installation with Amiad water strainer seen at the back. New pump station with VFD-circulation pumps connected to the 100 000ℓ buffer tanks.

THE PROBLEM

“Our existing cooling plant was quite dated,” explains Thomson. The old underground sump only had a 10 000ℓ capacity. Although this was effective in 1962 when the cellar was built, it no longer made sense to cool the tanks by running water over it. Instead, Weideman plates have been installed inside the tanks for cooling (all except the six rotor tanks at the red wine fermentation section).

However, with Eskom’s unreliable power supply, whenever the power went on and off, the whole sump would flood as the cellar was higher than the sump. All the cold water would then simply run off into the drains.

As a result, the sump was closed a few years back and a new bunker was built. The cooling towers were moved on top of the bunker. Previously, these towers had stood on the ground level, but this caused a problem in terms of dust as tractors were constantly driving past it.

As the wine cellar grew, so did the cooling load until it reached 2 012kW. However, the existing system only had a 1 336kW capacity, leaving a capacity shortage of about 676kW, explains Steven Palvi Jnr, operational manager at Wynroete Verkoeling, who was directly involved in the upgrade of the plant.

With a large shortage of cooling capacity to keep the water at the desired temperature, the existing chillers were running at full load during the entire pressing season. This meant that they were functioning at a minimum coefficient of performance (COP) and energy efficiency ratio (EER).

In this instance, the cooling towers were struggling to keep up because of the higher temperatures and thus gets clogged faster. High condensing temperatures caused higher compressor working temperatures, more wear and tear, and a higher pressure at which the motor had to pump. “It was drawing more amps but producing less cooling,” says Palvi Jnr.

Aermec glycol chiller equipped with shell and tube condensers and a brazed plate evaporator. Upgraded DB board done by Ferdi Hayes Panels (Rawsonville). First and second phase completed; 1456kWr at nominal conditions. New Aermec NXW0800Y chiller for glycol – 270kWr at nominal conditions, equipped with four R410a scroll compressors.

THE IMPORTANCE OF COOLING IN WINE-MAKING

When the grapes arrive at the cellar later in the day, the cellar’s temperature can go up as high as 36°C in the afternoon heat. “Grapes don’t want heat,” explains Thomson. “It’s fine if they’re still whole, but the moment it goes through the crusher, breaking the grape open and exposing the juice to oxygen, it becomes a nightmare. It turns brown and you lose your flavour. And that you can never get back, no matter what you do.”

That is why it is vital that as soon as the grape has been broken open, it has to go through some version of cooling. As such, mash coolers are installed to cool the product after the grapes have been broken open. This is where most of the cooling requirement comes from.

For the new pressing cellar, the offloading container’s mash cooler is situated very close to the point of entry. Within 5m of the mono pump, the product is inside the cooler — which is ideal. This mash cooler, made of stainless steel, is quite over-designed compared to the other older ones that have been around since 1962, explains Palvi Jnr.


Pull quote As the wine cellar grew, so did the cooling load until it got to 2 012kW. However, the existing system only had a 1 336kW capacity, leaving a capacity shortage of about 676kW.


The next phase will be to sell the older two mash coolers and replace them with more effective models. “There is nothing wrong with them, but they are ineffective as they are struggling to keep up with the new de-stemming machines that are much faster,” explains Thomson. These de-stemming machines are currently only running on 60% capacity on the V-drives, as the old mash coolers cannot cope with the faster speed. Thus, the full capacity available for offloading is not being maximised. The cooling to support these upgraded mash coolers is already in place.

The cooling system is fully operational from around 20 January until 20 April when the wine pressing takes place. The rest of the year, the only cooling needed is to keep the wine tanks cool. “The advantage is that if the cellar is cool inside, it is cool,” explains Thomson. “It takes quite a while for the wine to warm up again inside the cellar once it has been cooled.”

Open air (outside) blending and fermentation tanks.Tank temperature controller solenoid valve. 
Water gully. 
 
Cooling towers for water chillers situated on top of the 100 000ℓ chilled water buffer tank.

During the winter months, the cooling is switched off. They put the cooling on again mid-November to get the cellar cool before pressing starts.

But the cooling is not just used for the mash coolers. For wine-making, you require both warm stability and cold stability, explains Thomson. Warm stability comes into play when making the wine protein stable. “But the wine also has to be cold stabilised to get rid of the tartaric acid crystals,” he says.

There are cold stabilisation tanks complete with external insulation to cool the wine to about -4/-5°C, with mixers. Then, thanks to a seeding process, the crystals eventually lump together until the particles are large enough to sink to the bottom. Then the wine can be bottled without the risk of any build-up of crystals inside. For this process, the glycol system is used. That is why there are two systems, explains Palvi Jnr.

Since replacing the glycol machine (still operational from 1962), the cold stabilisation process has become much more effective in keeping up with the cooling demand, explains Thomson. “We save about four or five days on a cycle now as the wine is cooled down to temperature much quicker.” Because you can only seed the wine once it reaches 0°C, the pull-down time is very important to the process.

Because Du Toitskloof bottles a lot of its own wine, it has quite a large cold stabilisation facility compared to other cellars. It is cheaper for them to do the cold stabilisation process in-house than to do it at the bottling company.

They also offer services to outside parties who want to bottle their product — this will include the cold stabilisation. This is also a form of additional income. The cellar uses this to pay for general maintenance of the operation.

It is not just about cooling, though. “The other challenge we have, is getting the humidity right for the barrel room,” explains Palvi Jnr. If the humidity is too low, the wine will evaporate much faster from the barrels. This is the other part that needs to be controlled in terms of HVAC; however, it is being controlled without a humidifier. Instead, they use the condensation that builds up in the blower coil (instead of throwing it out). It has been set up so this water can run back into a gully in the cellar to improve the humidity.

Chilled water distribution lines with pressure-regulating valves. Product circulation pumps mounted to each tank. Settling tanks for juice preparation in the new facility. Tank temperature controller mounted to each wine tank.

UPGRADING THE PLANT ROOM

When the tonnage of grapes that had to be processed grew from 12 000 to 16 000 tonnes, there simply was not enough cooling. “We couldn’t maintain the fermentation temperatures,” explains Thomson. “We couldn’t get the outside tanks under 18°C.” So, in 2014, they asked the Wynroete Verkoeling team, with whom they have had a long-standing relationship, to present a new solution.

“The phase out of R22 refrigerants also played a role,” explains Palvi Jnr. “It was time to upgrade the equipment either way.” The new machines all run on R134a refrigerant.

The Wynroete team reviewed quite a few options in terms of chillers and selected the Aermec solution. The first 728kW unit was installed in 2014 and was a WF2812A high-efficiency chiller. The second was the 720kW WF2812, which was commissioned in February 2017. Both these chillers are fitted with Bitzer screw compressors. The glycol chiller (270kWr nominal) that was supplied is a NXW0800Y, producing 175kW at -5°C, and is fitted with Copeland scroll compressors. This unit was also commissioned in February 2017.

Although Wynroete offered the client various options, the Aermec chillers were selected because of the extended three-year warranty, its price, and its satisfactory EER, explains Palvi Jnr. They did all the heat load calculations prior and got the stamp of approval from a consultant before going ahead.

However, everything could not be replaced at once, so the upgrade was scheduled in stages. Firstly, they removed the old Trane unit still in operation from 1962, as well as a newer reciprocating Daikin machine that was installed sometime in the 1990s.

The glycol machine is set at -5°C and the chilled water temperature at 7°C.

Chilled water return line.  Stainless steel piping for product distribution between the phases. Stainless steel mash cooler.

PHASE TWO

Space is availabe for expansion and new machinery in the plant room.

The new pressing cellar is still incomplete, and the new phase will require an extra chiller for the cooling.

When the new cellar is complete, the aim is to handle 20 000 tonnes. But this is all still a work in progress.

For now, the Du Toitskloof team is very happy with their cooling solution and ready for the 2018 season’s intake.

List of professionals

 Owner    Du Toitskloof wine cellar 
 Project manager    Windmeul Projects 
 Contractors  HVAC&R   Wynroete Verkoeling 
 Product suppliers  Chillers  Aermec (Aersa) 
 Glycol chillers   Aermec (Aersa)
 Cooling towers   IWC 
 Pumps   Rapid Allweiler (supplied by Wynroete)
 Compressors   Bitzer
 Copeland 
 PVC and stainless steel works  Vinco Steel

 


Click below to read the January 2018 issue of RACA Journal

RACA JAN2018

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