Properties of Torrefied U.S. Waste Blends

Zhuo Xu,Ezra Bar-Ziv,Dennis Conn,Armando G Mcdonald,Shreyas S Kolapkar,Stas Zinchik,Ted Hansen

doi:10.3389/fenrg.2018.00065

Zhuo Xu, Ezra Bar-Ziv + Show 5 more

Open Access

https://doi.org/10.3389/fenrg.2018.00065

Copy DOI

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 300oC 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.

Highlights

The U.S Environmental Protection Agency (EPA) has accelerated regulatory pressure on utilities burning pulverized coal by issuing carbon emission guidelines on June 18, 2014 (EPA, 2014)
To determine the regime that best fits the description of the system behavior, one should start with the analysis with Biot number (Bi) and thermal Thiele modulus (M); the former is related to the heating regime of the particle, and the latter relates to the propagation of the torrefaction reaction within the particle
The torrefied samples were characterized by moisture content, grindability, particle size distribution, energy content, molecular functional structure, and chlorine content

Summary

Introduction

The U.S Environmental Protection Agency (EPA) has accelerated regulatory pressure on utilities burning pulverized coal by issuing carbon emission guidelines on June 18, 2014 (EPA, 2014). The EPA has proposed state by state goals to achieve CO2 emission reductions; 30% from the power sector as compared to CO2 emission levels in 2005 (EPA, 2015). The ultimate fate and form of the EPA proposed rule may not be known for some time until the rule-making process is complete but the past history of utility emissions regulation and Supreme Court decisions on EPA rulemaking authority indicate a high probability that some form of CO2 regulation will be implemented (White, 2014). Kiel (Kiel, 2011) suggested the use of biomass for coal power plants. A considerable amount of studies, pilot-scale plants, patents and commercial efforts have been devoted to torrefaction and torrefied materials. The consensus is that the main hindrance to the commercialization of this technology is the use of high-cost woody biomass as a feedstock (Kumar et al, 2017; Radics et al, 2017)

Methods

Results

Conclusion