Rotating cone

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Rotating Cone Technology

The initial work of the University of Twente has been the basis for BTG [1] to further develop the pyrolysis reactor and the overall process. The researchers started with the principle that intense mixing of biomass and hot inert particles is the most effective way to transfer heat to the biomass, but that fluid bed mixing requires too much ineffective inert carrier gas. A high intensity reactor for the pyrolysis of biomass was developed where no inert gases were required, while simplifying the reactor parts and peripheral equipment as oil condenser, gas cleaning etc. The original idea in 1989 to rely on a merely ablative principle without inert sand was modified later to a sand transported-bed rotating cone reactor (RCR). The concept is depicted on the right side. Instead of mixing the biomass in hot sand fluidized bed driven by inert gas, the pyrolysis reactions take place upon mechanical mixing of biomass and sand. Similar to CFB operation, the sand and char are further transported to a separate fluid bed where the combustion of char takes place. The RCR enables a high solids throughput and short vapor residence times. RTD work was continued by BTG Biomass Technology Group, first to about 50 kg/hr in 1997. Here, a cone reactor is integrated in a circulating sand system composed of a riser, a fluid bed char combustor, the RCR reactor, and a down comer. Char is burnt in the combustor to generate the heat required for the pyrolysis process, viz. by (re-)heating the inert sand that is re-circulated to the reactor. Oil is the only product of this lab facility, and gases were flared. In 2001 the system was further scaled up to 250 kg/hr. In addition to this pilot plan installation, a smaller (5 kg/hr) test unit has been erected in BTG’s laboratories, for quick screening of potential feedstock materials in a continuously operated system. Initially, researchers reported that the RCR principle would be limited to particles < 1 mm in diameter. Over the years, however, the way of mixing in the cone and the pyrolysis system were improved considerably. The overall efficiency of the process is increased, the acceptable particle diameter demonstrated to be up to 10 mm, and product quality and consistency for different feed stocks are improved considerably. This led to the world’s first commercially sold unit of 50 t/d on so-called Empty Fruit Bunch (‘EFB’) in Malaysia.