Opportunities and Challenges of High-Pressure Fast Pyrolysis of Biomass: A Review

Abstract

Most pyrolysis reactors require small sizes of biomass particles to achieve high-quality products. Moreover, understanding the usefulness of high-pressure systems in pyrolysis is important, given the operational challenges they exhibit specific to various biomass materials. To actualize these aspects, the authors first checked previous reviews involving pyrolysis on different biomass and different conditions/situations with their respective objectives and subsections. From these already existing reviews, the team found that there has not been much emphasis on high-pressure fast pyrolysis and its potential in biomass conversion, showing that it is a novel direction in the pyrolysis technology development. Therefore, this review aims to shed more light on high-pressure fast pyrolysis, drawing from (a) classification of pyrolysis; (b) reactors used in fast pyrolysis; (c) heat transfer in pyrolysis feedstock; (d) fast pyrolysis parameters; (e) properties/yields of fast pyrolysis products; (f) high pressure on pyrolysis process; (g) catalyst types and their application; and (h) problems to overcome in the pyrolysis process. This review increases the understanding regarding high-pressure fast pyrolysis. An attempt has been made to demonstrate how high-pressure fast pyrolysis can bring about high-quality biomass conversion into new products. It has been shown that fluidized bed (bubbling and circulating) reactors are most suitable and profitable in terms of product yield. The high-pressure, especially combined with the fast-heating rate, may be more efficient and beneficial than working under ambient pressure. However, the challenges of pyrolysis on a technical scale appear to be associated with obtaining high product quality and yield. The direction of future work should focus on the design of high-pressure process reactors and material types that might have greater biomass promise, as well understanding the impact of pyrolysis technology on the various output products, especially those with lower energy demands. We propose that the increase of process pressure and biomass particle size decrease should be considered as variables for optimization.

Study on the Effect of Hydrothermal Carbonization Parameters on Fuel Properties of Chicken Manure Hydrochar

“…Another benefit of HTC is that there is no need for manure drying, which is directly related to the emission of odors. The hydrothermal conversion process of recycling organic waste or biomass in general usually begins at the temperature range of 160 and 300 C [8,9,14]. Largely, this depends on the type of hydrothermal treatment and purpose of any given (hydrothermal conversion process-based) project.…”

“…Largely, this depends on the type of hydrothermal treatment and purpose of any given (hydrothermal conversion process-based) project. Generally, the hydrothermal treatment process comprises different categories, namely: hydrothermal carbonization or liquefaction (HTC/L) [8,14,15]. These types could also be classified based on operational conditions.…”

“…Variations in pressure and temperature facilitate the solvent's interaction between intermolecular forces [22], there are liquefaction aspects, where the involved biomass undergoes reactions such as depolymerization, decomposition, and recombination, which are dependent on the reactive nature. Previous reviews about thermal conversion [8] have emphasized the fundamental processes/mechanisms involving HTC, where various research needs, and characterization of products have led to the identification of its deemed importance in industrial applications.…”

“…Waste generated in poultry farms, such as droppings and litter could pose human health risks [6]. In the wake of climate changes and energy shortages, there is an increasing need for new ways of providing clean and sustainable energy [7,8]. In this sense, creating an alternative use of poultry manure for energy production purposes while mitigating its inherent effect on the environment is warranted, for instance, the application of thermochemical conversion processes such as pyrolysis, gasification, and direct burning of poultry manure to provide sustainable fuel [9].…”

“…´ (8) where: MYmass yield, %; mhmass of dry hydrochar after HTC process, g; mrmass of dry raw material before HTC process, g; EDr energy densification ratio, %; HHVhhigh heating value of hydrochar after HTC process, Jg -1 ; HHVrhigh heating value of raw material before HTC process, Jg -1 ; EYenergy yield, %.…”