STiR coffee and tea magazine

Volume 4, Number 2

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30 STiR tea & coffee industry international / Issue 2, 2015 (April/May) This graphic shows air flows and heat transfer within a Regenerative Thermal Oxidizer (RTO). Diagram courtesy of Anguil Environmental Solutions approach with coffee is to apply more heat. Afterburners are typical for small roasters. Larger plants may employ catalytic or regenerative oxidizers instead. All three rely on some amount of heat in the oxidation process. These methods are preferred to some other technical innovations because roasting exhaust, to those who specialize in air pollution remediation, is "dirty." Scott Bayon, director of sales at Anguil, noted, "What's in the exhaust from a coffee roaster is typically a strong odor, condensable organic oils and chaff. We know the particulates (chaff) and oils will be an issue in oxidizer selection." For many, the simple application of more heat to oxidize by incineration is falling out of favor because of high fuel costs. The other two oxidizer types, catalytic and regenerative, use less gas: catalytic because it operates at a lower temperature and re- generative because it captures and reuses heat before it escapes the system. Anguil has been selling oxidizers since 1978 with approxi- mately 1,800 units deployed worldwide. More than half of those are catalytic because many of the company's early customers were bakeries. Bayon explained that this type of oxidizer tends to weigh less in addition to not needing as much heat to operate. Many commercial bakeries like both characteristics because the most logical location for installing pollution control equipment in these businesses is often on the roof. Though property constraints may dictate oxidizer choices for bakery settings, coffee companies more often seek to re- duce operating costs. Catalytic oxidizers operate at lower tem- peratures but rely on a consumable catalyst for oxidation to take place. Those consumables are precious metals that need to be replaced every 2-3 years. "You could [spend] as much as $20,000 to $30,000 [replac- ing the catalyst] in these units," Bayon said. Some European roasting equipment suppliers have devel- oped products and system designs that incorporate one or both approaches to reducing pollutants and greenhouse gas precur- sors from roast exhaust. According to Koziorowski, nearly all of Probat's industrial roasting systems utilize a process that recirculates the smoke from roasting back to the burner and reheats it to roasting temperature. The Proforte uses a flameless, regenerative, thermal oxida- tion process to meet the lowest emission guidelines. "Here the roasting exhaust gases are led through a ceramic bed whose in- terior has temperatures of 900 to 1,100°C," according to Probat. Probat's entire range of exhaust air cleaning technology, including the thermal pre-cleaners, is modular, explains Kozi- orowski — this facilitates cost-effective retrofitting of a catalytic afterburner, for example, to meet ever-changing emission rules. He explained the benefit to a roaster operating in Germany: "When using a thermal pre-cleaner with catalytic afterburner, the [target] value for the total carbon content of the roasting exhaust air as per German air pollution control regulation - com- monly referred to as 'TA Luft' - is [met]." Bayon said that, "RTOs are the most popular oxidizer tech- nology across almost all industrial applications due to the high internal heat recovery and associated reduction in gas consump- tion. The catalytic oxidizer is limited to a maximum internal heat recovery rate of about 65% — RTO will achieve 95%." When asked if there were innovations happening with RTOs, Bayon reported that some advances have been made with the materials, ceramic plates mostly, which act as heat sinks. These and other advances have the effect of upping what Koziorowski called the "thermal degree of efficiency" to above 95%. In the case of the Proforte from Probat, the thermal efficien- cy ranges from 95-98%. Most RTOs have a minimum of two chambers with ceramic beds. To function properly, the system needs to warm up. This requirement may make RTOs less desir- able for companies that do not roast seven days per week. Pre- heating the oxidizer once a week erodes fuel efficiency savings. But for a large facility that does operate every day? Bayon said, "That's really the whole point of the RTO, to minimize fuel costs. If you look at a commercial roaster using just an incinerator, you could easily be talking about hun- dreds of dollars an hour in gas just to run those incinerators. Whereas an RTO might [cost] $10 per hour, it's that drastic [a difference]." Rapid Change in Asia European citizens and companies are far from the only people struggling to keep up with changes in environmental and industrial rules. Chinese air pollution is so pervasive that companies there are having difficulty keeping foreign talent according to a 2014 report from Reuters. Two other stories are garnering a lot of attention online. Quartz India published a story by Saptarishi Dutta with the headline "Don't Take a Breath - India's toxic air is taking away three years from your life." "China's Haze," a documentary by a former television anchor for China Central Television was released on Youku and as of this writing had not yet been censored.

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