Low Maintenance Nitrogen Generator Helps Winery Protect Flavor

The use of a nitrogen generator that requires virtually no maintenance is helping Arkansas’ largest winery protect the flavor of its diverse product line. The winery purges the air from every bottle of wine and fills it with nitrogen, which protects the wine from oxygen that would otherwise slowly turn the wine to vinegar. In the past, the winery had to bear the high cost of purchasing compressed nitrogen in cylinders. More recently, it took advantage of the availability of relatively inexpensive nitrogen generators that separate the nitrogen from the other constituents in air as needed in the bottling process. “The key factor in selecting a nitrogen generator was that we didn’t want to take on an expensive and complicated maintenance task,” said Andrew Post, Winemaker at the Post Familie winery. “After looking for a while, I found a machine that operates without any maintenance or attention at all for a period of five years. At that point, you change the filter and it’s ready to go for another five years. This generator has provided completely trouble-free performance, allowing me to focus on what I like to do best, making great wine.”

In 1872, Jacob Post left his home in Baden-Baden, Germany, where his family made wine, and moved first to Illinois and then to Arkansas. He immediately began selling wine the next year, which makes Post Familie the oldest commercial vineyard between California and New York. The winery is a family endeavor. Jacob’s daughter in law, Katherine Post, won notoriety for serving 18 months in federal prison for violating prohibition and, according to family lore, after returning home said: “That was the best vacation of my life!” Seven of the twelve children of Katherine’s grandson Mathew Post presently work in the winery though all of them have worked the farm and winery while growing up in Altus. Currently there are 200 acres of grapes in production at Post and the company made 180,000 gallons of wine last year. The unique climate in the company’s home of Altus, Arkansas, which once had 40 operating wineries, makes it possible to grow all five of the major winemaking grape species. Post produces 45 different varieties of wine at price points ranging from $3.75 to $18 per bottle. In the last 20 months, the company has won 20 gold, 16 silver and 20 bronze medals in various competitions around the world.

Need for an oxygen-free bottle
Bottling is done in the main winery building using state of the art equipment. A Gai bottle rinser is used to remove anything that might have fallen into the bottle during shipment such as lint or dust from its container. A Krones filler is designed to first flush the air from the bottle and then fill it with wine. The company has a Bertalosa corker and Alcoa and Resina cappers. The reason that air is flushed out of the bottle before filling is that oxygen in the air is the enemy of wine. Oxygen enables the growth of bacteria naturally present in grapes that can turn the alcohol in wine into acetic acid, giving it a vinegary taste and eventually turning it into wine vinegar. Wine's fermentation process is usually oxygen-free because of the large amount of carbon dioxide produced when yeasts turn sugars into alcohol. But removing the oxygen from the bottle is a must in order to preserve the flavor of the wine. Some winemakers fill the bottle with carbon dioxide but the wine tends to absorb a considerable amount of carbon dioxide which can also have a negative impact on the flavor of many types of wine.

The traditional approach to obtaining the nitrogen used during the bottling process has been to purchase large cylinders filled with compressed nitrogen. “We were spending far too much money paying for nitrogen and as our production volume increased our expenses also rose at a steady rate,” Post said. “Another problem with purchasing nitrogen was that we had to pay close attention to how much gas we had left because if we ran out that meant shutting down our bottling line.” Gas cylinders also require careful handling because the gas is confined under very high pressures and there is also a risk of injury involved in handling the heavy metal cylinders. The winery purchased a 150 cubic feet per hour nitrogen generator several years ago but outgrew it over several years. The problem was that as the company approached the 150,000 gallons per year production rate, the nitrogen generator could no longer keep up with our bottling line. So the company would frequently have to shut down the bottling line to wait for the nitrogen generator to catch up.

Selecting a maintenance-free nitrogen generator
“It was clear that we needed a larger generator,” Post said. “I checked out three different models that were all capable of providing the capacity that we needed. The thing I was most concerned about was the maintenance that would be required. All of the machines use one of two methods to separate the nitrogen from air, membrane separation technology used for low purity applications and PSA (pressure swing adsorption) for higher purity applications. Most of them require that the filters and other pretreatment componentry be changed quite frequently, especially the prefilters that are used to remove impurities from the air prior to separation. On the other hand, one of the nitrogen generators, the Balston MB-400 Pressure Swing Absorption (PSA) nitrogen generator (from Parker Hannifin Corporation, Filtration and Separation Division, Tewksbury, MA) only needed its prefilters changed once every 12 to 18 months, with no moving parts, no other maintenance was required. This was exactly what I was looking for, a nitrogen generator that I could buy, turn on and then forget about. I talked to a few users of this nitrogen generator and they spoke highly of it and the price was right so we decided to buy the Balston unit.” Post selected an MB-400 model that produces 433 standard cubic feet per hour of 95% pure nitrogen or 200 standard cubic feet per hour of 99.95% pure nitrogen. The unit is 56 inches wide by 42 inches deep by 89 inches high and weighs about 1800 pounds.

Parker Balston PSA nitrogen generators utilize a combination of filtration and pressure swing absorption technologies. High efficiency prefiltration treats the compressed air to remove all contaminants down to 0.01 micron. Air entering the generator consists of 21% oxygen and 78% nitrogen. The gas separation process preferentially adsorbs oxygen over nitrogen using a carbon molecular sieve (CMS). Molecular sieves are devices with discrete pore sizes that can discriminate between molecules on the basis of size. An essential feature of CMS’s is that they provide molecular separations based on rate of adsorption rather than differences in adsorption capacity. At the same conditions, the rate of adsorption is made up of at least two important factors, the equilibrium uptake or capacity of the sieve and the diffusivity or rate of diffusion of the porous material. It is the relative diffusivity that determines the rate of molecular sieving. CMS’s offer stability at high temperatures, low affinity to water and their pore sizes can be controlled by the method of preparation. At high pressures the CMS has a greater affinity for oxygen, carbon dioxide and water vapor than it does at low pressures. By raising and lowering the pressure within the CMS bed, all contaminants are captured and released, leaving the CMS unchanged. This process allows the nitrogen to pass through as a product gas at pressure. The depressurization phase of the CMS releases the adsorbed oxygen and other contaminant gases to the atmosphere.

Parker Balston PSA nitrogen generators produce up to 99.95% pure, compressed nitrogen from nearly any compressed air supply. Installation consists of simply connecting a standard compressed air line to the inlet and connecting the outlet to a nitrogen line. Then the electrical cord is plugged into a wall outlet and the unit is ready for operation, 24 hours per day, 7 days per week. Once the unit is operating, it requires little monitoring. The only maintenance involves changing the coalescing prefilter cartridges and final sterile air filter about once per year. The PSA towers do not require any maintenance. An optional oxygen monitor measures the oxygen concentration of the nitrogen stream. An audible alarm signals high or low oxygen concentration and is also supplied with relay outputs.

“The Balston nitrogen generator has performed exactly as advertised,” Post concluded. “The 433 cubic feet per hour of nitrogen that it delivers is considerably more than we need to operate our bottling line at full capacity. As a result, we have eliminated the need for nitrogen-related shutdowns since we installed the new generator. So far, the machine has required no maintenance and I expect that we should easily go for five years before we have to do anything. By eliminating these concerns, the nitrogen generator has allowed us to concentrate our attention on making a high-quality, wholesome product and delivering it to wine lovers around the world.”

For additional information on Balston® products, contact Parker Hannifin Corporation, Filtration and Separation Division, 100 Ames Pond Drive PO Box 1262,Tewksbury, MA 01876-0962. Tel: 800-343-4048 Fax: 978-858-0625 Web site: www.parker.com/ags.