Double-screw reactor

The cationic copolymerization of trioxane with ethylene oxide, 1,3-dioxolane, and suchlike is initiated either with strong protonic acids or Lewis acids, for example BF3. Molecular weight is controlled by the catalyst concentration and monomer purity, and also by chain transfer agents such as methylal [248], which may lead to more stable end groups. Most processes are run below the melting temperature of the polymer (164-167°C) in precipitating agents or in bulk, and are carried out in kneaders or double-screw reactors [249, 250], but there are also some descriptions of melt processes [251]. 

Double screw auger behave more like back-or cross-mix reactors ... 

Figure 4.30 Scheme for polyether polyol fabrication by anionic polymerisation of alkylene oxides, initiated by glycerol or diols (variant). 1 - Reactor for potassium glycerolate synthesis 2 - Reactor for prepolyether synthesis 3 - Reactor for polyether synthesis 4 - Reactor for purification 5 - Filter press 6 - Storage tank for final purified poly ether 7 - Heat exchangers for removal of the reaction heat 8 - Condensers 9 - Vacuum pumps 10 - Vessels for distilled water 11 - Recirculation pumps 12 - Gear pump or screw (or double screw) pump... 

The Biolig process of the research center Karlsruhe FZK, Germany. Here, flash pyrolysis, with emphasis on straw as feedstock, is tested to produce a bio-oil-char slurry. The pyrolysis reactor compares to the ER reactor (Lurgi-Ruhrgas) by which sand as heat carrier is mixed and transported together with biomass in a double (twin) screw feeder. A novel unit is constructed with a biomass processing capacity of 12 t/day. 

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