Flash pyrolysis reactors

Schematic overview of flash pyrolysis reactor technologies. (Reproduced from Meier, D., and Faix, O., Wood and Biomass Utilization for the Carbon Uptake, Seoul National University, 2005. With permission.)...

Description of the process. The process involves the utilization of two separate CFBs, both operated at ambient pressure (Figure 16.11). The first is a flash pyrolysis reactor in which waste is converted with the addition of steam, at a temperature between 700 and 900°C, into product gas and tar. The reducing atmosphere avoids the dioxins formation. The prodnct stream, made of fuel gas and HCl in a composition strongly dependent on feed/steam ratio, is quenched to recover HCl, which is then further purified. The second CFB is a combustor that provides heat for flash pyrolysis by burning the residnal tar the... 

Two of the flash pyrolysis reactors used for the experiments were fabricated from Amersil T08 commercial grade 50 mm OD quartz tube, and one from 25 mm OD vycor tube (Corning Glass Co.). The flow straightener/female joint was made of quartz for one of the 50 mm OD reactors, and pyrex for the other two reactors. The feeder was made primarily from plexiglas. Teflon tube (6 mm ID) was used to connect the reactor to the pyrex tar trap. 

Most promising is flash pyrolysis in which fuel particles are heated very rapidly (more than 1,000 °Cs ) and remain in the hot zone for a very short time (in general less than 1 s). After this very short time period, the liquid compounds produced from the solid biomass by decomposing the organic compounds (z.e. lignin, celluloses) have to be removed and cooled rapidly to avoid further decomposition into gases. To date, flash pyrolysis reactors have reaehed laboratory stage development level and the first pilot plants are available. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

A process of polymerization of isomerized a-pinene or turpentine with vinylbenzenes has been disclosed (105). a-Pinene or turpentine is isomerized by flash pyrolysis at 518 5° C in a hot tube reactor to yield a mixture of predominantly dipentene and i7t-alloocimene... 

Fig. 9. Lurgi-Rhurgas flash pyrolysis system, where 1 is a lift pipe 2, primary pyrolysis reactor 3, screw feeder 4, secondary pyrolysis reactor 5 and 7,...

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. 

Various reactor configurations for flash pyrolysis have been developed [37-39] ... 

As stated previously, optimal temperatures and residence times are needed for maximal bio-oil production, which could be achieved in so-called fast or flash pyrolysis, when the residence time of the pyrolysis vapors and the optimal temperature are 0.1-2 s and between 400°C and 650°C, respectively [12, 13], with the optimum being usually approximately 500°C [14], Reactors where the optimal pyrolysis conditions can be achieved include the following [11, 13, 15, 16] ... 

The carbonization of polypropylene is similar to that of polyethylene. During slow pyrolysis of polypropylene and for a temperature increase from 400 to 700°C, the yield in the liquid phase remains higher than 80% with a very small increase in the yield of gas phase (less than 20%). On the other hand, in flash pyrolysis of polypropylene, an increase of temperature from 550 to 700°C leads to a decrease of the yield in the liquid phase down to 40% with an increase of the gas phase up to 60%. As presented for PE (see Section 2.1), Sawagushi et al. [21] present the results of steam gasification of PP in a fixed bed reactor (Figure 10.8). 

Free-fall reactors (FFR) are a good choice for rapid or flash pyrolysis. They have been widely harnessed to pyrolyze coal and, more recently, biological mass. A pioneering group at Ankara University was the first to attempt pyrolysis of waste plastics in a FFR. Then-results are very promising indeed compared with other alternatives in the literature. 

A FREE-FALL REACTOR SYSTEM FOR FLASH PYROLYSIS... 

Figure 23.7 The temperature effects on product phase yields of PS. (Reproduced from Journal of Analytical and Applied Pyrolysis, 60 (2), A. Karaduman, Flash pyrolysis of polystyrene wastes in a free-fall reactor under vacuum, 179-186(2001), with permission from Elsevier)...

H. Er ahan and A. Y. Bilgesu, Products from flash pyrolysis of Turkish lignite in a free-fall reactor under vacuum. Fuel Sci. Techn. Int, 12, 1475 (1994). 

The splitting of the cyclonic combustor into reactors is shown in Figure I. The corresponding reactor network accepted in the combustion modeling is shovm in Fig. 2. The reactor network structure is largely based on the current understanding of the processes in the combustor issuing from the limited experimental observations and from the CFD calculations [4], The key assumption is a separation of the biomass pyrolysis and subsequent char and gas oxidation, Thus, the initial part of the network represents flash pyrolysis of the biomass. 

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