Vortex reactor heating biomass

Ultrafast pyrolysis in the vortex reactor is capable of pyrolyzing biomass at high heat-transfer rates on the reactor wall by ablation and has been... 

This chapter describes the initial results of converting waste sawdust into phenolics through fast pyrolysis employing a vortex reactor and a very fast heat transfer to depolymerize biomass into monomeric and oligomeric components. The pyrolysis method and the chemical fractionation employed to isolate the phenolic-rich fraction used in the subsequent adhesive gel testing are described. Results of an economic evaluation of the process are presented as well as the characterization of the phenolic-rich material. A novolak and a resol were successfully prepared with these compounds. 

Much of the pioneering work on ablative pyrolysis reactors was performed by CNRS at Nancy where extensive basic research has been carried out onto the relationships between pressure, motion and tenperature (23). NREL developed an ablative vortex reactor (see Figure 6 and (14)), in which the biomass is accelerated to supersonic velocities to derive high tangential pressures inside a heated cylinder. Unreacted particles are recycled and the vapours and char fmes leave the reactor axially for collection. Liquid yields of 60 65%wt. on dry feed basis are typically obtained. 

A vortex tube has certain advantages as a chemical reactor, especially if the reactions are endothermic, the reaction pathways are temperature dependent, and the products are temperature sensitive. With low temperature differences, the vortex reactor can transmit enormous heat fluxes to a process stream containing entrained solids. This reactor is ideally suited for the production of pyrolysis oils from biomass at low pressures and residence times to produce about 10 wt % char, 13% water, 7% gas, and 70% oxygenated primary oil vapors based on mass balances. This product distribution was verified by carbon, hydrogen, and oxygen elemental balances. The oil production appears to form by fragmenting all of the major constituents of the biomass. 

As with any other reactor that is based on heating biomass by contacting it with a hot surface, the vortex rector pyrolysis is surface area-controlled. That means the scale-up of these systems is very difficult, and they are t3 pically only used for small scales. 

Ablative reactors are those in which heat transfer takes place primarily by solid-solid contact. In these reactors, biomass particles or entire wood rods are heated up by direct contact with a hot metallic surface. The solid-solid contact is an advantage from the perspective of increasing heat transfer rates. The main drawback with these reactors, however, is that the process is limited by the surface area of contact, which makes the scale-up very difficult. Ablative reactors should only be considered for small-scale applications. The main ablative reactors are the vortex (or cyclone) reactor and the cone reactor. 

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