Properties of Torrefied U.S. Waste Blends

Abstract

Power generation facilities in the U.S. are looking for a potential renewable fuel that is sustainable, low-cost, complies with environmental regulation standards and is a drop-in fuel in the existing infrastructure. Although torrefied woody biomass, meets most of these requirements, its high cost, due to the use of woody biomass, prevented its commercialization. Industrial waste blends, which are also mostly renewable, are suitable feedstock for torrefaction, and can be an economically viable solution, thus may prolong the life of some of the existing coal power plants in the U.S. This paper focuses on the torrefaction dynamics of paper fiber-plastic waste blend of 60% fiber and 40% plastic and the characterization of its torrefied product as a function of extent of reaction (denoted by mass loss). Two forms of the blend are used, one is un-densified and the other is in the form of pellets with three times the density of the un-densified material. Torrefaction of these blends was conducted at 300 • C in the mass loss range of 0-51%. The torrefied product was characterized by moisture content, grindability, particle size distribution, energy content, molecular functional structure, and chlorine content. It was shown that although torrefaction dynamics is of the two forms differs significantly from each other, their properties and composition depend on the mass loss. Fiber content was shown to decrease relative to plastic upon the extent of torrefaction. Further, the torrefied product demonstrates a similar grinding behavior to Powder River Basin (PRB) coal. Upon grinding the fiber was concentrated in the smaller size fractions, while the plastic was concentrated in the larger size fractions.

Bypassing Energy Barriers in Fiber-Polymer Torrefaction

“…The materials in this study were waste industrial paper wastes, MPW and commercially available LDPE (Rainier Plastics), cellulose powder (Avicel PH-101, ∼50 µm particle size, Fluka) as well as hemicellulose (extracted xylan). The paper wastes and MPW have been described in detail in the prior studies (Xu et al, 2018;Xu et al, 2020). The paper wastes are a mixture of paper, carton and cardboard, label matrix residuals, wax papers, and laminated non-recyclable papers; and the plastic wastes consist of LDPE, PE, polyethylene-terephthalate (PET), polyamide-nylon, polyvinylchloride (PVC), PP, and some other materials.…”

“…Therefore, the heat convection from the oven to the sample surface is much slower than the heat conduction into the sample; for M << 1, it indicates that the heat conduction into the sample is much faster than the reaction rate. Thus, the particle temperature throughout was uniform and equals to the gas temperature (which is measured), and the reaction rate was governed by the heat convection from the oven to the surface of the sample (Xu et al, 2018).…”

“…Torrefaction has been proposed as a process for thermal chemical conversion of various feedstocks to increase the heating value and make the material more friable (Chen and Kuo, 2011;Chen et al, 2015;Chen et al, 2019;He et al, 2018;He et al, 2019;Xu et al, 2018). The synergies between biomass and plastics during thermochemical conversion have also been well explored in the past decades (Chattopadhyay et al, 2008;Han et al, 2014;Olajire et al, 2014;Zhang et al, 2016;Burra and Gupta, 2018;Chen et al, 2020).…”

Pyrolysis of Fiber-Plastic Waste Blends

“…We note that we will flow fiber and plastic flakes that are 10×10 mm, with a thickness of <1 mm into the reactor. We also note that when either fiber and plastic flakes are torrefied they become very brittle as seen by Zhuo et al [93] and can be grinded rather easily by the paddles that act as blades. Indeed, in the 1inch reactor (as well as in the batch reactor) the char was in the form of a very fine powder.…”

Advances in Biomass Co-Combustion with Fossil Fuels in the European Context: A Review

“…Xu et al (2018) [92] studied physical properties of various waste material blends after their torrefaction in a convective furnace at 300 • C and exposure time of 3 to 120 min. They concluded that, depending on the material type, its heating value remained the same or increased, and the material loss was up to 55%.…”