Ultrasonic Vibration-Assisted Pelleting of Cellulosic Biomass for Biofuel Manufacturing: A Study on Pellet Cracks

Author(s):  
Yongjun Tang ◽  
Pengfei Zhang ◽  
Defu Liu ◽  
Z. J. Pei ◽  
Weilong Cong

Biofuels produced from cellulosic biomass are an alternative to petroleum-based liquid transportation fuels. The costs of cellulosic biofuel manufacturing are high partly due to the low density of raw cellulosic materials. Processing cellulosic biomass into pellets can increase density and handling efficiency of cellulosic feedstocks, resulting in reduction of transportation and handling costs. The literature on ultrasonic vibration-assisted (UV-A) pelleting includes studies about effects of pelleting parameters on pellet quality, pelleting temperature, charring, and sugar yield. However, there are no studies on pellet cracks. This paper, for the first time, presents a study on pellet cracks in UV-A pelleting of wheat straw. It first describes experimental conditions and then presents experimental results about effects of pelleting parameters on crack size. Afterward, it proposes a hypothesis on crack formation in UV-A pelleting and discusses some evidences that support this hypothesis. Finally, it provides explanations to experimental results based on the hypothesis.

2012 ◽  
Vol 151 ◽  
pp. 245-249 ◽  
Author(s):  
Yong Jun Tang ◽  
Chun Mu Chen ◽  
Guan Wang

Cellulosic biofuels have been proposed to replace part of traditional liquid transportation fuels. Cellulosic biomass is the feedstock in cellulosic biofuel manufacturing. Costs associated with collection and transportation of cellulosic biomass account for more than 80 percent of the feedstock cost. By processing cellulosic biomass into pellets, density and handling efficiencies of cellulosic feedstock can be improved, resulting in reduction of transportation and handling costs. The pellet temperature is one of the most important parameter in Ultrasonic Vibration (UV-A) pelleting. There is very few literature on the pellet temperature of UV-A pelleting. This paper mainly studied how to on-line measure the pelleting temperature, also, the detailed temperature characteristics of the pellet was obtained. The results are valuable for selecting suitable pelleting parameters and controlling the quality of pellet in UV-A pelleting. Also, the accurate measurement of the pellet temperature is helpful to understand pelleting mechanism, charring, and durability issues.


Author(s):  
Qi Zhang ◽  
Pengfei Zhang ◽  
Meng Zhang ◽  
Xiaoxu Song ◽  
Z. J. Pei ◽  
...  

Biofuels made from cellulosic biomass are an alternative to petroleum-based liquid transportation fuels. However, low density of cellulosic biomass causes high costs in biomass transportation and handling in cellulosic biofuel manufacturing. Such costs can be reduced by pelleting processes that can densify cellulosic biomass. Ultrasonic vibration-assisted (UV-A) pelleting and ring-die pelleting are two pelleting methods. A previous study has compared the two pelleting methods in terms of pellet quality and pelleting power consumption. This paper reports an experimental comparison on sugar yields of wheat straw processed by the two pelleting methods under different combinations of pretreatment variables. Results show that wheat straw processed by UV-A pelleting has higher sugar yield than that processed by ring-die pelleting when the higher temperature and longer time are applied in pretreatment. Under other combinations of pretreatment variables, wheat straw processed by UV-A pelleting has lower sugar yield than that processed by ring-die pelleting.


Author(s):  
Hera Wu ◽  
Pengfei Zhang ◽  
Qi Zhang ◽  
Z. J. Pei

Cellulosic biofuels are an alternative to petroleum-based liquid transportation fuels. However, manufacturing costs of cellulosic biofuels are high partially due to low density and sugar yield of cellulosic biomass. Previous studies show that UV-A pelleting can increase the density and sugar yield of cellulosic biomass. A hypothesis for UV-A pelleting to increase the density and sugar yield of cellulosic biomass is that UV-A pelleting can reduce biomass particle size. To test this hypothesis, biomass particle sizes before and after UV-A pelleting need to be compared. Soaking pellets in water is an efficient and non-invasive method to separate pellets into particles. However, water soaking itself might change biomass particle size. This paper reports an investigation on effects of water soaking on biomass particle size. The biomass particle sizes before and after water soaking are measured and compared. Results show that effects of water soaking on biomass particle size are dependent on the initial particle size (particle size before water soaking) and time period of water soaking.


Author(s):  
Qi Zhang ◽  
Pengfei Zhang ◽  
Z. J. Pei ◽  
Graham Pritchett ◽  
Meng Zhang ◽  
...  

Cellulosic biomass is abundantly available in the nature. It is an attractive feedstock to make alternative fuels to petroleum-based transportation fuels. Because of low bulk density and irregular shape, raw biomass materials are difficult to handle, transport, and store. Pelleting can increase the density of cellulosic biomass. Pellets can be easily handled, resulting in reducing their transportation and storage costs. Ultrasonic vibration-assisted (UV-A) pelleting is a new pelleting method. Moisture content, particle size, pelleting pressure, and ultrasonic power are four important input parameters affecting pellet quality and sugar yield (proportional to biofuel yield). However, their effects on power consumption in UV-A pelleting have not been adequately investigated. Since power consumption directly affects ethanol manufacturing costs, it is desirable to understand how input parameters affect power consumption. This paper reports an experimental investigation of power consumption in UV-A pelleting. A 24 factorial design is employed to evaluate the effects of four input parameters (moisture content, particle size, pelleting pressure, and ultrasonic power) on power consumption in UV-A pelleting. Results show that three input parameters (moisture content, particle size, and ultrasonic power) significantly affect power consumption. Higher moisture content, lower ultrasonic power, and larger particle size result in higher power consumption. Only one interaction of two parameters is significant, i.e. with the increase of pelleting pressure, power consumption will increase at the high level of particle size while decrease at the low level of particle size.


Author(s):  
Qi Zhang ◽  
P. F. Zhang ◽  
Timothy Deines ◽  
Z. J. Pei ◽  
Donghai Wang ◽  
...  

Cellulosic biofuels can be used to replace traditional liquid transportation fuels. Cellulosic biomass is feedstock in manufacturing of cellulosic biofuels. However, the low density of cellulosic biomass feedstock hinders large-scale and cost-effective manufacturing of cellulosic biofuels. Another bottleneck factor in manufacturing of cellulosic biofuels is the low efficiency of the enzymatic hydrolysis of cellulosic biomass materials resulting in a low sugar yield. Ultrasonic vibration-assisted (UV-A) pelleting can increase the density of cellulosic biomass feedstocks via combined effects of mechanical compression and ultrasonic vibration of the tool on the cellulosic biomass. Meanwhile ultrasonic vibration may act as a beneficial pretreatment for enzymatic hydrolysis, which can possibly increase the efficiency of hydrolysis and obtain a higher sugar yield. The pressure and the ultrasonic power are important parameters in UV-A pelleting. Their effects on pellet quality (density, durability, and stability) and sugar yield (after hydrolysis) are experimentally investigated.


2013 ◽  
Vol 805-806 ◽  
pp. 151-155
Author(s):  
Kang Qi Fan ◽  
Yong Jun Tang ◽  
Yang Fang

Increasing concerns about reliable supplies and envi­ronmental consequences of petroleum-based fuels have made it important to develop sustainable green sources for liquid transportation fuels. One such source is cellulosic biomass. However, high costs associated with transportation and storage of low-density cellulosic biomass has hindered large-scale, cost-effective manufacturing of cellulosic biofuels. Ultrasonic vibration-assisted (UV-A) pelleting can increase biomass density, improve storability, and reduce transportation costs. This paper reviews the state of the art of this technique, covering the effects of different process parameters on pellet quality, pellet charring, pellet crack, and sugar yield. It can be concluded that pellet density increases with an increase in ultrasonic power and pelleting pressure, and with a decrease in biomass moisture content and particle size. However, large ultrasonic power may lead to the charring of cellulosic biomass, which adversely affects the conversion of cellulosic biomass to ethanol. In addition, some problems associated with UV-A pelletingof cellulosic biomass are proposed.


Author(s):  
Z. J. Pei ◽  
Donghai Wang ◽  
Robert Clark

Biofuels produced from cellulosic biomass (such as the fibrous, woody, and generally inedible portions of plant matter) can significantly reduce the nation’s dependence on foreign oil, create new jobs, improve rural economies, reduce greenhouse gas emissions, and improve national security. However, in the U.S., there are currently no cellulosic biofuel plants in commercial production. Several technical barriers have hindered large-scale cost-effective manufacturing of cellulosic biofuels. One such barrier is related to the low density of cellulosic feedstocks, causing their transportation and storage to be very expensive. Pelleting biomass can increase the overall efficiency by utilizing existing transportation infrastructure and storage systems for mega-ton quantities. If biomass is pelleted, it can be handled and transported with existing grain handling equipment in the field, on the road, and at the central biorefinery. This paper presents experimental study on ultrasonic vibration assisted pelleting of cellulosic feedstocks. The results show that ultrasonic vibration assistance could increase the mechanical strength of pellets by more than six times and the density by 50%.


2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Meng Zhang ◽  
Xiaoxu Song ◽  
Pengfei Zhang ◽  
Z. J. Pei ◽  
T. W. Deines ◽  
...  

Increasing demands and concerns for reliable supply of liquid transportation fuels make it important to find alternative sources to petroleum-based fuels. Cellulosic biofuels provide one such alternative in the short to medium term. Size reduction is the first step for converting biomass into biofuels. In the literature, there are inconsistent reports about the effects of particle size and biomass crystallinity on sugar yield (proportional to biofuel yield). An important reason for this inconsistence is that particle formation in current size reduction methods is not well controlled, causing the effects of these two variables confounded. One paper investigating the confounding effects of particle size and biomass crystallinity using a metal-cutting (milling) process was previously published in this journal. This paper presents a follow-up study. In this study, a lathe was used to produce poplar wood particles with the same crystallinity but different sizes, making it possible to study the effects of particle size on biofuel yield independently without being confounded by the effects of biomass crystallinity. Results showed that, for the three levels of particle size used in this study, sugar yield increased as particle size became smaller. This study also revealed future research opportunities to understand the effects of size reduction and biomass crystallinity in cellulosic biofuel manufacturing.


Author(s):  
Qi Zhang ◽  
Pengfei Zhang ◽  
Graham Pritchett ◽  
Z. J. Pei ◽  
Meng Zhang ◽  
...  

Ethanol produced from cellulosic materials is an alternative to petroleum-based transportation fuels. However, its manufacturing costs are too high to be competitive at present. Raw cellulosic biomass materials have low density, causing their transportation and handling expensive, contributing to high manufacturing costs of cellulosic ethanol. Pelleting can increase the density of cellulosic biomass and reduce their transportation and handling costs. Ultrasonic vibration-assisted (UV-A) pelleting is a new pelleting method. Earlier studies show that moisture content and particle size have significant effects on pellet quality and sugar yield. However, their effects on power consumption in UV-A pelleting have not been studied. Since power consumption directly affects ethanol manufacturing costs, it is desirable to understand how input variables affect power consumption. The objective of this paper is to study effects of moisture content and particle size on power consumption in UV-A pelleting of wheat straw. Results show that higher moisture content and larger particle size result in higher power consumption.


Author(s):  
Meng Zhang ◽  
Xiaoxu Song ◽  
P. F. Zhang ◽  
Z. J. Pei ◽  
T. Deines

Gradual depletion of world petroleum reserves and increasing environmental impact of greenhouse gas emissions make it urgent to develop sustainable alternatives to petroleum-based transportation fuels. Cellulosic biofuels provide one such alternative in the short to medium term. In order to convert cellulosic biomass into biofuels, size reduction is a necessary step. In the literature, there are inconsistent reports about the effects of particle size and biomass crystallinity on sugar yield (proportional to biofuel yield). An important reason for this inconsistence is that particle formation in current size reduction methods is not well controlled, causing the effects of these two variables confounded. This paper presents an experimental study on size reduction of poplar wood using a lathe, where particle formation could be well controlled to prevent the effects of these two variables from being confounded. In this study, particle size was controlled by different numbers of slots cut on the workpiece. Particles with the same crystallinity but different particle sizes were produced. This will make it possible to study the effects of particle size on biofuel yield independently, and reveal future research opportunities to understand the effects of size reduction in cellulosic biofuel manufacturing.


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