This paper introduces a closed-loop dryer system to reduce the energy consumption for milk powder production. The system is based on a monodisperse droplet atomizer which reduces the amount of fines in the exhaust air, and allows dehumidification and recirculation of the air over the dryer. In this way the latent and sensible heat from the dryer exhaust are recovered. Two adsorbent systems for dehumidification are discussed; a membrane contactor with a liquid desiccant, and a zeolite sorption wheel. Four configurations for closed-loop spray drying are simulated and optimized. By heat integration of the adsorber-regenerator system with the dryer and preceding concentration step, the energy consumption is significantly reduced to 4.9 MJ heat per kg milk powder. The final heat integration solutions were obtained by simultaneous optimization of the operational conditions and the heat exchanger network based on pinch analysis.

Industrial relevance

Drying is an energy intensive operation in processing. To comply with the upcoming regulations that arise from the EU goals for sustainable development, the energy consumption of drying processes should be reduced drastically. Emerging technologies are the key for the next step in energy efficiency improvement. A closed-loop spray drying system for milk powder production is simulated and optimized in this work. The proposed technologies are: monodisperse droplet drying, membrane contactor and a zeolite wheel. By applying air dehumidification and heat integration the latent and sensible heat are recovered from the exhaust air. The energy consumption for milk concentration and spray drying has the potential to be lowered from 8.4 to 4.9 MJ heat per kg milk powder. Although milk powder has been considered, the proposed system is also applicable to other food products, as well as in the (bio)chemical, pharmaceutical and paper industry.

中文翻译：

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闭环喷雾干燥解决方案，用于高效节能的粉末生产

本文介绍了一种闭环干燥机系统，以减少生产奶粉的能耗。该系统基于单分散液滴雾化器，该雾化器减少了废气中的细粉量，并允许除湿和空气在干燥机上的再循环。这样，干燥机排气中的潜热和显热就被回收了。讨论了两种用于除湿的吸附剂系统。带有液体干燥剂和沸石吸附轮的膜接触器。模拟并优化了闭环喷雾干燥的四种配置。通过将吸收器-蓄热器系统与干燥机进行热集成，并进行预先的浓缩步骤，可将能耗显着降低至每千克奶粉4.9兆焦耳热量。

行业相关性

干燥是加工中的能源密集型操作。为了遵守欧盟可持续发展目标中即将出台的法规，应大幅减少干燥工艺的能耗。新兴技术是下一步提高能效的关键。在这项工作中，模拟并优化了用于奶粉生产的闭环喷雾干燥系统。提出的技术是：单分散液滴干燥，膜接触器和沸石轮。通过对空气进行除湿和热集成，可以从废气中回收潜热和显热。牛奶浓缩和喷雾干燥的能耗可以从每公斤奶粉中的8.4兆焦耳降低到4.9兆焦耳。尽管已经考虑了奶粉，