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Seductively clean – Air Pollution Control in the cocoa industry

Bietigheim-Bissingen, 1st of April 2011. In recent years, different air pollution control technologies have repeatedly been tested in the cocoa industry. Tests with scrubbers and biofilters did not bring about the desired results whereas thermal technologies, such as regenerative oxidizers, proved to be efficient and cost-effective. These systems are characterized by high destruction and energy efficiency advantages.

Dürr Environmental and Energy Systems' regenerative oxidizer is the most efficient pollution control system to meet the specific requirements of the cocoa industry, as far as pollutants and odors are concerned.
Harvesting and processing the cocoa beans to eventually make chocolate is a long and tedious process. Cocoa seeds initially taste extremely bitter, and their typical, palate pleasing flavor does not appear until roasted. After roasting, the roasted beans are ground and processed further.
Subsequently, odors, volatile organic compounds, and other gaseous pollutants emitted during the blending and roasting processes need to be treated before being exhausted to atmosphere. The emission issue is similar for the manufacturing of cocoa, coffee or similar products such as chicory.  Typically, these processes are characterized by varying exhaust air volumes with different compositions (e.g. VOCs, acids, fats, aerosols, ammonia, particles, dust), strong odors, and high water vapor levels.
Recently, two renowned cocoa producers were faced with this compliance issue.  One of these companies planned a new production line in Germany while the other engineered for additional emission reduction for an existing production line located in France. After thoroughly comparing and considering possible solutions, and running comprehensive pilot tests, both producers ended up opting for Dürr pollution control technology.
Dürr relies on proven technology, namely regenerative oxidizers, in use in other application areas that have comparable compliance requirements. Regenerative oxidizers are particularly reliable because these types of systems ensure high system uptime reliability which is very important for food industry and its 24 hour production schedules. In addition, regenerative oxidizers require little maintenance and upkeep. Their low energy use allows them to run efficiently and maintain a high destruction efficiency well into the future.
However, the high levels of fats, aerosols, and particles, typical of cocoa production emissions, could eventually cause a standard system to break down and thus reduce its efficiency. The customer-specific solution was to pre-treat air for small exhaust air volumes or to use a very sturdy plant design for large air volumes.
Accordingly, a Dürr Ecopure® RTO 3050 regenerative oxidizer was started up in 2010 at the customer's plant in Germany. The system has an extremely long-lasting and rugged design and is not prone to breakdowns caused by a great variety of pollutants. This level of sturdiness is achieved by a special valve design, a self-cleaning bake-out cycle, the physical composition of the equipment (anti-corrosion stainless steel in this instance), a high quality refractory lining, and many other features. The plant's modular design enables a production capacity increase at a later time. High energy efficiency is achieved by the choice of heat exchanger material in connection with a flameless burner system.
In the other case, the customer in France registers a much smaller exhaust air flow rate. For this reason, a regenerative compact thermal oxidizer, a Dürr Ecopure® CTO, is used. In combination with the highly efficient electrostatic precipitators used to remove particles and aerosols, a major part of the fats contained in the air are recycled. The cleaned condensate coming out of the fat separator can be discharged to the factory's waste water treatment plant without causing any further environmental problems. This combination of technologies has been implemented for the first time globally and allows regenerative thermal oxidation to be built simply and cost effectively for small exhaust volumes too.
Both plants have been running for a few months now, and initial measurements show that the required limits are met, and in some cases,  far exceeding expectations.
In the future, regenerative oxidation technology will be inevitable in the food industry. Strict emission and odor control requirements call for high-quality solutions. Simpler technologies such as scrubber systems or biofilters are unable to meet the numerous requirements in many cases. On the basis of its diverse RTO technologies, Dürr is capable to customize an energy-efficient solution.