Ultrasonic-Assisted Pelleting of Sorghum Stalk: Predictive Models for Pellet Density and Durability Using Multiple Response Surface Methodology

Qi Zhang,Jiping Zhou,Xi Chen,Pengfei Zhang,Zhenzhen Shi,Zhichao Li,Meng Zhang

doi:10.3390/en11051214

Abstract

In the field of renewable energy, feedstock such as cellulosic biomass has been proposed as a renewable source of fuel to produce energy. However, the use of raw biomass as feedstock causes high costs in handling, transportation, and storage. Compressing raw cellulosic biomass into pellets significantly increases the density and durability of cellulosic biomass, reducing the transportation and handling costs of feedstock. To ensure high pellet quality, high pellet density and durability are desired during a compressing process. In this study, ultrasonic vibration-assisted (UV-A) pelleting, as a novel pelleting method, was applied to measure pellet density and durability during experiments. Response surface methodology (RSM) was employed to investigate the effects of pelleting time, ultrasonic power, and pelleting pressure on the pellet density and pellet durability. The model was validated by comparing the predictive results with experimental data and demonstrated a good predictive ability (R2 > 0.95). By employing a Derringer and Suich’s desirability function, our results suggest that the optimal pellet density and durability are 1239 kg/m3 and 93%, respectively, when the pelleting time was set to 44 s, the ultrasonic power was set to 50%, and pressure was set to 42 psi (289,580 Pa).

Highlights

Extensive usage of petroleum transportation fuels has urged research in renewable energy to seek strategies which can provide the reliable supply of liquid transportation fuels and reduce greenhouse gas emissions [1,2,3,4]
As the ultrasonic power increased from 25% to 50%, the pellet density for various levels of pelleting pressure increased when the pelleting time equaled to 45 s
By incorporating experimental data from the designed experiment into nonlinear models, the proposed method can predict the effects of pelleting time, pelleting pressure, and ultrasonic power on the pellet density and durability

Summary

Introduction

Extensive usage of petroleum transportation fuels has urged research in renewable energy to seek strategies which can provide the reliable supply of liquid transportation fuels and reduce greenhouse gas emissions [1,2,3,4]. In the United States, more than 30% of the current petroleum consumption can be replaced by cellulosic ethanol [5]. This type of replacement could ameliorate the long-lasting environment issues and economic burden. There are some barriers to achieving cost-effective cellulosic ethanol manufacturing. A major barrier is the low density of cellulosic biomass, ranging from 40 to 250 kg/m3 [7], which causes high expenses during handling, transportation, and storage. Pelleting, which compresses biomass into a uniform shape and size of pellets can significantly increase the density of cellulosic biomass over

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Conclusion