Ultrasonic Vibration-assisted Pelleting Research Articles

Process Optimization of Pellet Manufacturing from Mixed Materials in Ultrasonic Vibration-Assisted Pelleting

Achieving carbon neutrality and alleviating the rural energy predicament are crucial aspects in rural areas, particularly in the severe cold regions of northeast China. Pellets serve as clean, renewable energy sources and are ideal alternative fuels. This study investigated the influencing factors and effects of mixed raw materials in ultrasonic vibration-assisted pelleting (UV-A pelleting). Rice straw and corn stover were mixed to produce pellets, and a central composite rotatable design (CCRD) was conducted to analyze the variables and their interactions on pellet density and durability. Mathematical regression models for pellet density and durability were established and then validated through ANOVA analysis. The results showed that all variables significantly affected the density and durability of pellets. The mixing ratio had a greater impact on pellet durability compared to density due to differences in ingredients. The optimal combination of process parameters included a mixing ratio of 25%, molding pressure of 4 MPa, pelleting time of 37 s, and ultrasonic power output at 200 W, resulting in a pellet density of 1301.18 kg/m3 with a durability reaching 94.26%. The desirability value (0.997) under these optimal conditions confirmed the validity of the models; further experiments also verified their effectiveness. The combustion of the optimized pellet was analyzed using thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis in an air atmosphere. Four combustion stages and ignition temperature were provided.

The Effect of Urea Pretreatment Combined with Ultrasonic Vibration-Assisted Pelleting on Pellet Solid Density and Durability

The Effect of Urea Pretreatment Combined with Ultrasonic Vibration-Assisted Pelleting on Pellet Solid Density and Durability

Optimization of density and durability of pellets using the response surface methodology in ultrasonic vibration-assisted pelleting of corn stover

Optimization of density and durability of pellets using the response surface methodology in ultrasonic vibration-assisted pelleting of corn stover

A Review on the Effects of Pretreatment and Process Parameters on Properties of Pellets

The development and utilization of biomass can not only address the demand for low-carbon energy and reduce environmental pollution, but can also facilitate the achievement of carbon neutrality. However, there are many factors justifying the case for low utilization of agricultural residues. These factors could be well controlled by producing top-quality pellets. Production of pellets is generally accompanied by the problems of high energy consumption and serious mold wearing. To eliminate these deficiencies, pretreatment has attracted scholars’ attention. In this review, the effects of four pretreatments on the properties of pellets were assessed. Thermal pretreatment can improve the hydrophobicity of pellets, and optimize their properties, while degradation of diverse extractives is noteworthy. Hydrothermal pretreatment improves the physical properties of pellets, through the increase of polar functional groups on the surface of the biomass. Ultrasonic vibration-assisted (UV-A) pelleting produces pellets under low pressure without a heating process; however, it is still not applied to large-scale production. Supercritical fluid extraction can achieve the graded utilization of extracts and bioactive substances in biomass, and the residues can be subsequently utilized as pellet feedstock. Mild hydrothermal treatment is a promising approach to improving the quality of agricultural pellets. Additionally, the effects of process parameters on the physical and chemical properties of pellets should be systematically analyzed.

Effects of different pretreatment methods on biochar properties from pyrolysis of corn stover

To explore the effects of pretreatment methods including drying, vacuum freezing drying (VFD), pelleting, and ultrasonic vibration-assisted pelleting (UV-AP) on corn stover and biochar properties, the physicochemical and morphological changes of biomass before and after pretreatment were examined, and the effects of different pretreatment methods on biochar properties were investigated. The results showed that different pretreatment methods have a significant effect on the surface and internal structure of biochar. The highest and lowest specific surface area, micropore area, and total pore volume of biochar were 25.84 m2/g, 9.27 m2/g, 0.53 cm3/g, and 17.33 m2/g, 4.39 m2/g, 0.29 cm3/g, respectively. FTIR analysis showed that the functional group of pretreated corn stover was similar to those of biochar. Ultimate analysis indicated that both pretreatment methods and the highest treatment temperature had a significant effect on biochar compositions. The order of carbon content of biochar derived from different pretreatment methods was drying > VFD > UV-AP > pelleting. The biochar yield, enhancement factor, and energy yield were significant affected by pretreatment methods. By contrast, the biochar pH was alkaline and not significantly affected by pretreatment methods. These findings provide a reliable route to choose pretreatment methods for producing biochar with desired properties, which could be a guide for industrial application.

Effect of ultrasonic vibration-assisted pelleting of biomass on biochar properties

The objective of this research was to investigate the potential of ultrasonic vibration-assisted (UV-A) pelleting as pretreatment method to produce biochar with desired properties. In this study, poplar (PP), switchgrass (SG), and wheat straw (WS) were pretreated with UV-A pelleting process, then the biochar were produced in a muffle at atmosphere condition with a highest temperature treatment (HTT) at 300, 500, and 700 °C, respectively. Ultrasonic power had an obvious effect on the biochar yield and pH, a higher biochar yield and biochar pH were obtained from PP00, SG50, and WS50 and PP50, SG50, and WS00, respectively. The FTIR spectra showed that O–H stretching, C–H stretching, carbonyl bonds/CO stretching, C–H stretching, C–O–C, and C–C stretching were found in spectra of UV-A pretreated biomass, while disappeared in spectra of biochar, indicating the changes of functional groups. Although UV-A pelleting pretreatment did not show considerable effect on the C, H, N, and S content of biochar (less than 2%) under the same HTT, the formation of multi-layer and porous structure was observed on biochar surface. The specific surface area, micropore surface area, and total pore volume of biochar from UV-A pelleting increased with increasing of ultrasonic power. In addition, HTT and type of biomass also had different functions on the biochar properties. The results of this study showed that UV-A pelleting pretreatment has a great potential to produce biochar with desired chemical structures and physical properties.

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

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).

Predictive temperature modeling and experimental investigation of ultrasonic vibration-assisted pelleting of wheat straw

Ethanol made from cellulosic biomass is an alternative to petroleum-based liquid transportation fuels. However, large-scale manufacturing of cellulosic ethanol is hindered by several factors. The main factor driving this hindrance is the low density of cellulosic biomass. Ultrasonic vibration-assisted pelleting can effectively increase cellulosic biomass density by compressing raw biomass into pellets, reducing transportation and storage costs. Pelleting temperature has also been identified as a key parameter influencing pellet quality. In this paper, a predictive mathematical model of pelleting temperature using spatio-temporal dynamics was developed to study multiple factors affecting temperature rise through pelleting. The mathematical model was then validated with experimental data along with high goodness of fit (average R2>0.83). Effects of three input variables (ultrasonic power, pelleting pressure, and pellet weight) on temperature ranges (highest temperature point and lowest temperature point) were investigated using a 23 (two levels and three variables) factorial design. Our results indicated that friction between mold and biomass has a marginal effect on the temperature profiles, and demonstrated the highest and lowest temperature points are significantly correlated to the input variables (ultrasonic power, pellet weight, and pellet pressure) and their interaction effects. The proposed mathematical model delivers a new guideline by avoiding unnecessary experiments and provides a systematic understanding of temperature profiles during the biomass pelleting process. Knowledge transferred from the current study fulfills the literature gap between mathematical modeling research and an optimal, ultrasonic, vibration-assisted pelleting process; and, therefore, provides insight into improving biomass quality in energy-related ultrasonic manufacturing.

Investigation on characteristics of corn stover and sorghum stalk processed by ultrasonic vibration-assisted pelleting

Cellulosic ethanol produced from cellulosic biomass is an alternative to petroleum-based liquid transportation fuels. The cost-effectiveness of cellulosic ethanol manufacturing has been hindered by several technical barriers. One such barrier is that low density of biomass causes high costs of biomass transportation, handling, and storage. Another barrier is low sugar yield in enzymatic hydrolysis, making enzymatic hydrolysis an expensive and slow step. Ultrasonic vibration-assisted (UV-A) pelleting of cellulosic biomass can increase its density and reduce the costs of biomass transportation and handling. In addition, sugar yield of biomass pellets processed by UV-A pelleting was higher than that of particles (unpelleted biomass) with diluted acid pretreatment. The reason that UV-A pelleting could increase sugar yield of biomass is still unclear. The objective of this study was to investigate reasons that UV-A pelleting combined with diluted acid pretreatment could increase sugar yield of biomass. High sugar yield is preferred to achieve high ethanol yield. Effects of UV-A pelleting on biomass characteristics (such as chemical composition, crystallinity index, thermal properties, and morphological structure) were investigated. The results showed there was no significant difference in chemical composition between pellets and particles. However, crystallinity of biomass increased after UV-A pelleting. In addition, pellets had higher decomposition temperature than particles, indicating that pellets were more thermally stable than particles. Examinations on morphological structure of biomass showed that softened surface regions of biomass were removed and cellulose microfibrils were revealed after UV-A pelleting.

Investigating pellet charring and temperature in ultrasonic vibration-assisted pelleting of wheat straw for cellulosic biofuel manufacturing

Biofuels are only alternative solution for liquid transportation fuels among different kinds of renewable energy. To avoid the competition with the food, cellulosic biomass has been proposed as feedstock for manufacturing of cellulosic biofuels. Costs associated with collection, transportation, and storage of cellulosic biomass account for more than 80% cost of the feedstock. By processing cellulosic biomass into high density pellets, handling efficiency of cellulosic feedstocks can be improved, leading to costs reduction in transportation and storage. Ultrasonic vibration-assisted (UV-A) pelleting is a recently developed pelleting method, which can not only produce higher density but also break the lignin shell, to some extent, to increase cellulose accessibility and then increase sugar and biofuel yield. The reported investigations on UV-A pelleting provided little information about the relationship between charring and pelleting temperature under different input variables of pelleting. In this paper, effects of different input variables of pelleting on both charring ratio and pelleting temperature were studied. This paper, for the first time, reported the relationship between charring ratio and pelleting temperature. The obtained results will be helpful in understanding the mechanism of UV-A pelleting and providing guide to control pellet charring for a higher biofuel yield.

Ultrasonic vibration-assisted pelleting of cellulosic biomass for ethanol manufacturing: An investigation on pelleting temperature

Ethanol made from cellulosic biomass is an alternative to petroleum-based liquid transportation fuels. However, large-scale manufacturing of cellulosic ethanol is hindered by the low density of cellulosic biomass. Experiments have shown that ultrasonic vibration-assisted (UV-A) pelleting could compress low-density raw biomass into high-density pellets, and pelleting temperature increased during pelleting process. However, pelleting temperature was not fully investigated. This paper reports an investigation on pelleting temperature in UV-A pelleting of wheat straw. The precision of temperature measurement was first evaluated. Relationships between pelleting temperature and pelleting time were then investigated. Also, the pattern of pelleting temperature distribution was evaluated by ranking the pelleting temperatures at six different locations in a pellet. Finally, effects of three input variables (ultrasonic power, pelleting pressure, and pellet weight) on pelleting temperature were discussed. Results reported in this paper are the foundation of a follow-up paper reporting relationship between pelleting temperature and pellet quality (density, durability, and sugar yield).

Ultrasonic vibration-assisted (UV-A) pelleting of wheat straw: A constitutive model for pellet density

Ultrasonic vibration-assisted (UV-A) pelleting can increase cellulosic biomass density and reduce biomass handling and transportation costs in cellulosic biofuel manufacturing. Effects of input variables on pellet density in UV-A pelleting have been studied experimentally. However, there are no reports on modeling of pellet density in UV-A pelleting. Furthermore, in the literature, most reported density models in other pelleting methods of biomass are empirical. This paper presents a constitutive model to predict pellet density in UV-A pelleting. With the predictive model, relations between input variables (ultrasonic power and pelleting pressure) and pellet density are predicted. The predicted relations are compared with those determined experimentally in the literature. Model predictions agree well with reported experimental results.

Comparison of two pelleting methods for cellulosic ethanol manufacturing: ultrasonic vibration-assisted pelleting vs. ring-die pelleting

Cellulosic ethanol made from cellulosic biomass is a sustainable alternative to petroleum-based liquid transportation fuels. One of the major challenges to cost effectiveness of cellulosic ethanol manufacturing is low density of raw cellulosic biomass that causes high costs of biomass transportation and storage. Pelleting can significantly increase biomass density,resulting in reducing the transportation and storage costs. Ring-die pelleting, a traditional pelleting method, generally involves high-temperature steam and high pressure, and often use binder materials. Ultrasonic vibration-assisted (UV-A) pelleting is a new pelleting method without using high-temperature steam, high pressure, and binder materials. This paper reports an experimental study to compare pellet quality (density and durability), sugar yield, temperature, energy consumption, microstructure of corn stover processed by UV-A pelleting and ring-die pelleting with two level of sieve size (3.2 and 9.5 mm). Results showed that pellets produced by UV-A pelleting had comparable density, durability, and sugar yield as those produced by ring-die pelleting. UV-A pelleting required higher energy consumption than ring-die pelleting and produced higher temperature than ring-die pelleting.

Ultrasonic vibration-assisted pelleting for cellulosic biofuels manufacturing: A study on in-pellet temperatures

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 [1]. By processing cellulosic biomass into pellets, energy density and handling efficiency of cellulosic feedstock can be improved, resulting in reduction of transportation and handling costs. Ultrasonic vibration-assisted (UV-A) pelleting is one of important pelleting process which can make high quality pellets efficiently. The literature on UV-A pelleting covers studies about effects of input process parameters on pellet density, durability, sugar yield, charring, and pelleting force, but has little information about pelleting temperature. This paper presents an experimental investigation on effects of input variables on pelleting temperature. The pelleting temperatures at the different locations of a pellet were measured during pelleting using metal wire-typed thermocouples. Several pelleting parameters were varied to study their effects on pelleting temperature. Results obtained will be helpful in understanding why pelleting parameters affect pellet quality (density and durability), charring, and sugar yield.

Effects of ultrasonic vibration-assisted pelleting on chemical composition and sugar yield of corn stover and sorghum stalk

Cellulosic ethanol made from cellulosic biomass is an alternative to petroleum-based transportation fuel. The cost-effectiveness of cellulosic ethanol manufacturing has been hindered by several technical barriers. One such barrier is that low density of biomass causes high costs of biomass transportation, handling, and storage. Another barrier is low sugar yield in enzymatic hydrolysis, making enzymatic hydrolysis an expensive and slow step. Ultrasonic vibration-assisted (UV-A) pelleting of cellulosic biomass can increase its density and reduce the costs of biomass transportation and handling. The effects of UV-A pelleting on sugar yield of cellulosic biomass have not been fully investigated. The objective of this paper is to investigate effects of UV-A pelleting on chemical composition and sugar yield of cellulosic biomass. The effects were investigated with and without dilute acid pretreatment using corn stover and sorghum stalk. It was found that there was no significant difference in chemical composition between pelleted and unpelleted biomass whether they went through dilute acid pretreatment or not. After dilute acid pretreatment, cellulose recovery of pelleted biomass was significantly higher than that of unpelleted biomass. UV-A pelleting could significantly increase the sugar yield in enzymatic hydrolysis for both corn stover and sorghum stalk.

A physics-based temperature model for ultrasonic vibration-assisted pelleting of cellulosic biomass

Temperature in ultrasonic vibration-assisted (UV-A) pelleting of cellulosic biomass has a significant impact on pellet quality. However, there are no reports on temperature models for UV-A pelleting of cellulosic biomass. The development of a physics-based temperature model can help to explain experimentally determined relations between UV-A pelleting process variables and temperature, and provide guidelines to optimize these process variables in order to produce pellets of good quality. This paper presents such a model for UV-A pelleting of cellulosic biomass. Development of the model is described first. Then temperature distribution is investigated using the model, and temperature difference between the top and the bottom surfaces of a pellet is explained. Based on this model, relations between process variables (ultrasonic power and pelleting duration) and temperature are predicted. Experiments were conducted for model verification, and the results agreed well with model predictions.

Ultrasonic Vibration-Assisted Pelleting of Cellulosic Biomass: A Review

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.

Ultrasonic vibration-assisted pelleting of wheat straw: A predictive model for energy consumption using response surface methodology

Cellulosic biomass can be used as a feedstock for biofuel manufacturing. Pelleting of cellulosic biomass can increase its bulk density and thus improve its storability and reduce the feedstock transportation costs. Ultrasonic vibration-assisted (UV-A) pelleting can produce biomass pellets whose density is comparable to that processed by traditional pelleting methods (e.g. extruding, briquetting, and rolling). This study applied response surface methodology to the development of a predictive model for the energy consumption in UV-A pelleting of wheat straw. Effects of pelleting pressure, ultrasonic power, sieve size, and pellet weight were investigated. This study also optimized the process parameters to minimize the energy consumption in UV-A pelleting using response surface methodology. Optimal conditions to minimize the energy consumption were the following: ultrasonic power at 20%, sieve size at 4mm, and pellet weight at 1g, and the minimum energy consumption was 2.54Wh.

Effects of ultrasonic vibration-assisted pelleting of cellulosic biomass on sugar yield for biofuel manufacturing

Ultrasonic vibration-assisted (UV-A) pelleting can increase the bulk density of cellulosic biomass, thus reduce the feedstock transportation cost in cellulosic biofuel manufacturing. UV-A pelleting can also increase the biomass sugar yield in enzymatic hydrolysis. There are two major processes in the sugar conversion of cellulosic biomass: pretreatment and enzymatic hydrolysis. Sugar yield definition used in reported UV-A pelleting studies is enzymatic hydrolysis sugar yield. This definition is based on enzymatic hydrolysis this single process without considering the pretreatment process. In fact, converting cellulosic biomass into fermentable sugar (glucose) is the combined effort of pretreatment and enzymatic hydrolysis. There are no papers in the literature investigating whether UV-A pelleting could increase the total sugar yield when both pretreatment and enzymatic hydrolysis are considered. This paper reports the first study using total sugar yield to investigate the effects UV-A pelleting on biomass sugar yield. Experimental results show that, for all the four types of cellulosic biomass (wheat straw, corn stover, switchgrass, and sorghum stalk) used in this study, total sugar yield of biomass processed with UV-A pelleting was 30 to 43 % higher than that of biomass not processed with UV-A pelleting.

Ultrasonic vibration-assisted pelleting for cellulosic biofuel manufacturing: Investigation on power consumption

Cellulosic ethanol produced from cellulosic biomass is an alternative to petroleum-based transportation fuels. Raw cellulosic biomass has low density, causing high costs in their storage, transportation, and handling. Ultrasonic vibration-assisted (UV-A) pelleting can increase the density of cellulosic biomass. Effects of UV-A pelleting variables on pellet quality (density, durability, stability, and strength) and sugar yield have been reported. However, power consumption in UV-A pelleting has not been fully investigated. This paper presents an experimental investigation on power consumption in UV-A pelleting of wheat straw. Effects of input variables (biomass moisture content, biomass particle size, pelleting pressure, and ultrasonic power) on power consumption are investigated. Results show that power consumption in UV-A pelleting increases as moisture content and particle size decrease, and as pelleting pressure and ultrasonic power increase.