Particle Agglomeration of Biomass and Plastic Waste during Their Thermochemical Fixed-Bed Conversion

Abstract

The article provides state-of-the-art research on agglomeration processes during fixed-bed combustion and gasification of low-grade fuels such as biomass and waste (primarily plastic-containing waste). Such fuels demonstrate complex thermal behaviour: their decomposition and combustion are multistage, accompanied by phase transitions, and may lead to fixed-bed mechanical instability and the non-uniformity of air distribution over the cross-section. To clarify the role of physicochemical factors (fuel composition and properties, reactor conditions), data from different sources are compared. The review shows that the fixed-bed agglomeration regimes can, in a rough approximation, be classified by the sintering mechanism (due to the melting of the mineral part or the organic part), with the following search for each mechanism realisation conditions by comparing the fuel properties and characteristic temperatures. Attempts to theoretically describe and numerically simulate the agglomeration phenomenon as a change in the structure of a reacting dispersed medium are also considered: the main directions in which such approaches can be developed are indicated.

Performance of Corn Cob Combustion in a Low-Temperature Fluidized Bed

“…The use of such fuel becomes completely unattractive for heat producers, although its quantities are quite significant. During combustion in movinggrate or fixed-grate furnaces becomes complicated due to the high concentration of Cl, S, and alkali metals (K and Na) in such biomass, deposits rapidly begin to accumulate on the combustion surfaces, as well as slag accumulation on heat exchangers and slag accumulation caused by silicate (Si) melt on water-cooled walls [7]. According to Shao et al [8], potassium (K) evaporation from fuel starts from 650 • C, and the highest rates are reached at ~1000 • C. Other authors determined that at temperatures from 600 to 815 • C, evaporated potassium (K) reacts with chlorine (Cl) and forms potassium chloride (KCl), which participates in slagging and fouling and causes corrosive problems [9].…”