Reaction decoupling in thermochemical fuel conversion and technical progress based on decoupling using fluidized bed

Thermochemical conversion of fuels via pyrolysis/carbonization,cracking,gasification and combustion has to involve a number of individual reactions called attribution reactions to form an intercorrelated reaction network for any conversion process.By separating one or some attribution reactions from the others to decouple their interactions existing in the reaction network,the so-called reaction decoupling enables a better understanding of the complex thermal conversion process and further the optimization of the conditions for attribution reactions as well as the entire conversion process to realize advanced performances.The dual bed conversion and two-stage conversion are the two representative types of fuel conversion technologies developed in recent years based on reaction decoupling.Many technical advantages have been proven for such decoupling fuel conversion technologies,such as poly-generation of products,low-cost production of high-grade products,elimination of undesirable products or pollutants,easy operation and control,and so on.The treated fuels with decoupling conversion technologies mainly include solid biomass and coal,as well as liquid petroleum oil.This paper is devoted to reiteration of the reaction decoupling concept and further to reviewing the research,developments and successful applications of several decoupling fuel conversion technologies of two such types by using fluidized bed as their major reactors.

Pyrolysis characteristics of waste tire particles in fixed-bed reactor with internals

This study investigated the characteristics of pyrolysis for waste tire particles in the newly developed fixed-bed reactor with internals that are a central gas collection channel mounted inside reactor.And a few metallic plates vertically welded on the internal wall of the reactors and extending to the region closing their central gas collection pipe walls.Experiments were conducted in two laboratory fixed bed reactors with or without the internals.The results shown that employing internals produced more light oil at externally heating temperatures above 700℃due to the inhibited secondary reactions in the reactor.The oil from the reactor with internals contained more aliphatic hydrocarbons and fewer aromatic hydrocarbons,leading to its higher H/C atomic ratios as for crude petroleum oil.The char yield was relatively stable for two beds and showed the higher heating values(HHVs)of about 23 MJ/kg.The gaseous product of pyrolysis mainly consisted of H2 and CH4,but the use of internals led to less pyrolysis gas through its promotion of oil production.

Energy-saving strategy for a transport bed flash calcination process applied to magnesite

A transport bed flash calcination(TBFC)process applied to magnesite is systematically investigated through process simulation to optimize the energy-saving strategy.The high-temperature calciner flue gas is used to preheat the fed magnesite,while the sensible heat with the caustic calcined magnesia(CCM)product is cooled by air sent to the calciner.Pre-decomposition of magnesite during preheating is considered on basis of the kinetics measured using a micro fluidized bed reaction analyzer that allows the minimized effect of external diffusion on reaction.With staged fuel gas supply the TBFC process allows the equivalence ratios around 1.2 for combustion.The preferred arrangement of stages for magnesite preheating and CCM cooling are respectively 4 and 2,leading to the energy consumption of 4100 kJ/kg-CCM and the energy efficiency of 66.8%,which is almost doubly higher than the 33.9%of the conventional reverberatory furnaces(RF).The pre-decomposition occurs mainly in the 1st-stage preheater,and the maximal conversion is about 13%.Varying the stages of preheating appears more influential on the energy saving than varying the cooling stages,while residence time above 1 s in the preheaters has limited effect.