Fluidised bed reactors are however more difficult to design than fixed bed reactors. Design considerations include: (1) Setting the flow rate to achieve fluidisation (2) Ensuring that bubble size remains small during the fermentation. (3) Prevention of the cells from falling or "sloughing" off the particles. (4) Minimising particle damage. 4、絮凝细胞系统(Flocculated cell systems) In flocculated cell reactors, the cells are trapped in the reactor due to an induced or natural flocculation process. In flocculation cells tend to group together causing them to come out of solution and to sink towards the base of the reactor. Flocculated cell reactors are used widely in anaerobic waste treatment processes. In these reactors, the methanogenic and other bacteria form natural flocs. The flocs move due to the release of methane and carbon dioxide by the cells. The reactors are typically egg-shaped. Flocculated cell reactors 第五节 固定化细胞的应用