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Mathematical Modelling of Pressure Distribution along the Die of a Biomass Briquetting Machine
Abstract
The screw extruder briquetting die is critical to determining the
quality of biomass briquettes. In this study, mathematical models were
developed to study pressure distribution along the briquetting die using the hot
extrusion scheme and assuming a plug flow. Parametric analysis to determine
the effects of design variables on die pressure distribution was carried out by
simulation using developed mathematical models. Results showed that pressure
along the die entry decreases rapidly with high yield strength of compacted
biomass and with increased friction coefficient at the briquetting die interface.
As friction coefficient at the die interface increases, there is rapid decrease in
pressure along the length of the die. Parameters resulting in rapid pressure
decrease along the briquetting die length would result in increased die pressure
at the end of the screw extruder. The developed mathematical models and the
results obtained could significantly contribute to design of briquetting dies.
... High-pressure technologies utilize equipment, such as the screw press/extruder briquetting machine, mechanical piston presses, hydraulic piston presses, roller presses and pelleting machines [27]. Theoretical studies [28][29][30][31][32][33][34] have been carried out on some high-pressure densification technologies to understand the effect of design parameters on the operational performance of equipment. Similarly, empirical investigations have been carried out on some densification technologies using different biomass materials. ...
Biomass has a high potential to contribute towards resolving the energy deficit. Processing biomass into solid fuels enhances its use in various bioenergy conversion technologies. The quality of densified biomass depends on several variables. The investigation of the effect of densification parameters on briquette quality is necessary for process optimization. This study investigates the influence of die temperature (100, 120, 140 °C) and feeding speed (2.4, 2.9, 3.3 mm s−1) on the quality of briquettes produced from poplar using a hydraulic biomass briquetting machine. The density of the briquettes ranged between 746.7 and 916.8 kg m−3 , the mechanical durability ranged from 97.4 to 98.4%, and the water resistance index was between 91.6 and 96.1%. The results show that the temperature was statistically significant (p < 0.05) on the density, mechanical durability and water resistance of biomass briquettes. The feeding speed was statistically significant (p < 0.05) on the density and water resistance. The interaction of temperature and feeding speed was statistically significant (p < 0.05) on all properties considered. The results obtained in this study are useful for optimizing the quality of briquettes produced using the hydraulic piston press.
... Several works have been done to research into biomass briquetting in Nigeria. Recent works, which investigated various aspects of biomass densification and technologies involved, include Jekayinfa et al. [132], Ojolo et al. [252], Orisaleye et al. [133,134,[253][254][255], Orisaleye and Ojolo [256,257], Ojomo et al. [258], Dairo et al. [259], and Adeleke et al. [260]. Abdulkareem et al. [261] investigated the combustion characteristics of biomass briquettes while Umar et al. [262] investigated the application of briquettes to fish processing. ...
Nigeria is a developing country with an insufficient supply of energy to meet the continuously growing demand. However, there are several biomass resources available within the country. This paper presents a desk review, which investigates the potential resources for biomass energy generation within the country. Energy policies to aid biomass use as an energy source within the country were also reviewed. Biomass resources identified within Nigeria include forest residues, agricultural residues, human and animal wastes, aquatic biomass, and energy crops. However, several of the resources, particularly agricultural residues, have competing uses, such as livestock feed and soil rejuvenation. An estimation of the technical energy potential of the biomass resources revealed that about 2.33 EJ could be generated from the available resources in Nigeria. Agricultural residues have an energy potential of about 1.09 EJ, with cassava, maize, oil palm, plantain, rice, and sorghum being the major contributors. Animal wastes, municipal solid waste, and forest residues have energy potentials of 0.65, 0.11, and 0.05 EJ, respectively. The potentials of wood fuel and charcoal are 0.38 and 0.05 EJ, respectively. The study found that despite the available potential and existing policies, not much has been done in the implementation of large-scale bioenergy within the country. However, there has been laboratory and research-scale investigations. The review suggests that more policies and stronger enforcement will aid bioenergy development within the country. From the review, it has been suggested that the agricultural sector needs to be developed to generate more biomass resources. More research, development, and implementation have to be carried out on biomass resources and bioenergy generation processes. The production of non-edible energy crops in marginal lands should also be considered prime to the development of bioenergy within the country.
The screw briquetting machine has problems which have been attributed to poor design. There are limited theoretical studies targeted at solving problems of biomass briquetting machines. The briquetting die determines the final shape and quality of the biomass briquettes. The performance of the screw briquetting machine is also dependent on the design of the briquetting die. In this paper, mathematical models were developed to study the die pressure using a plug flow theory. Effects of die entry angle, die reduction ratio, length of briquetting die, biomass compact yield strength and friction on the die pressure were investigated using the models. Increasing the die entry angle, reduction ratio, compact yield strength and friction coefficient resulted in increase in the die pressure. Increase in length of briquetting die and friction coefficient also resulted in increase in the die pressure. Optimum die entry angle was dependent on the yield strength of compacted material and the friction coefficient at the interface between the die and the compacted material. This study is useful in developing improved screw briquetting machines.
Screw extruders are commonly used in the food and polymer industries. Scientifically designed screw extruders for biomass compaction equipment are required to limit the existing problems faced in the industry. In this study, models based on the plug flow theory were developed and used to analyse the screw extruder for biomass compaction. The approach for development of the plug flow model involves a traction-and-retardation based mechanism utilizing force balances only, in contrast to the force and torque balance of previous models. The pressure developed along the length of the screw extruder was exponential and affected by the friction coefficients at biomass material interfaces between the screw and barrel, the channel depth and helix angle. The movement of material in the compaction region is drag-induced and the screw speed, channel depth and helix angle determine the flow rate through the screw channel. The approach utilized in this study for the development of models could be extended to study other types of screw extruders with relative ease compared to earlier approaches based on the plug flow theory.
The design of efficient screw extruder biomass briquetting machines is important for the utilization of loose biomass materials from wood and agricultural wastes for the production of solid fuel. In this study, the effects of geometrical parameters (channel depth and helix angle) and operational parameters (friction coefficient, mass flow rate and speed) on the performance and design of the briquetting machine were investigated using a pressure model based on the plug flow theory. An analytical model, which utilizes the pressure model, was also developed from Archard’s wear law to investigate screw wear of biomass briquetting machines. The study on the pressure model showed that a shallow screw channel and small helix angle resulted in rapid pressure build-up along the screw extruder biomass briquetting machine. High friction at the barrel-material interface, low friction at the screw-material interface, high screw speed and high mass flow rate also resulted in rapid pressure build-up along the screw extruder biomass briquetting machine. The geometrical and operational parameters which resulted in rapid pressure build-up required shorter screw length for the briquetting machine. The wear model developed predicted the screw wear satisfactorily and showed that the screw speed and the choice of material for screw affected the screw wear. The wear volume increased exponentially towards the end of the screw where pressure is the highest. Redesigning the screw to select optimum geometry and speed with appropriate choice of material could improve the screw life and performance of the biomass briquetting machine. © 2019, Int. Comm. of Agricultural and Biosystems Engineering. All rights reserved.
India is an agrarian country with the abundant availability of biomass. Therefore, it is essential to make the best use of the biomass potential. It is indispensable to effectively use this resource so that the problem of energy could be eased. In order to accomplish this objective, an effective and efficient utilization of the biomass is the key. Biomass is the only source of energy that stores carbon into its structure and releases back into the environment upon the use. Uses of biomass for different application results into various operational, environmental, financial and even logistic issues. The aim of this chapter is to make the reader aware of the liberal spectrum of biomass available in general and India in particular. This chapter also presents the utilization of biomass under different technology pathways for various applications and operational issues are discussed. The data is helpful to arrive at the correct technology alternate for the use of a given biomass type.
Screw extruders are commonly used in the food and polymer industries. Scientifically designed screw extruders for biomass compaction equipment are required to limit the existing problems faced in the industry. In this study, models based on the plug flow theory were developed and used to analyse the screw extruder for biomass compaction. The approach for development of the plug flow model involves a traction-and-retardation based mechanism utilizing force balances only, in contrast to the force and torque balance of previous models. The pressure developed along the length of the screw extruder was exponential and affected by the friction coefficients at biomass material interfaces between the screw and barrel, the channel depth and helix angle. The movement of material in the compaction region is drag-induced and the screw speed, channel depth and helix angle determine the flow rate through the screw channel. The approach utilized in this study for the development of models could be extended to study other types of screw extruders with relative ease compared to earlier approaches based on the plug flow theory.
About eighty percent of Nigerians and sixty percent of Africans live in rural communities most of who utilize biomass for cooking. The benefits of improved cookstoves coupled with the perennial fuel crisis have led to intensified research into the development of the biomass cookstoves. This work aims to develop a biomass cookstove for use in developing countries. The biomass cookstove working with an inverted downdraft gasifier was developed and evaluated at Lagos State University, Nigeria. The biomass used was wood shavings with bulk density of about 0.05 g/cm 3 and with a moisture content of about 19.2% on dry basis and 16.2% on wet basis. The fuel conversion rate is 1.89 kg/h and it has a thermal effeciency of about 10.6%. The heating rate of the biomass cookstove was higher than the kerosene stove but less than the electric stove. While further work on the cookstove is recommended and proposed, the present and subsequent works can be adapted to suit rural applications where biomass is the major source of fuel but used inefficiently. The biomass cookstove cost $70 for a single unit but can be cheaper when mass produced.
The role of energy in the development of a nation cannot be underestimated. The current situation of energy in Nigeria reveals that an energy crisis is pending in the country. However, there is an abundance of renewable energy resources in Nigeria most of which have remained untapped. This paper gives an estimate of the technical potential of biomass energy in Nigeria, the technical potential being the part of the theoretical energy which can be harnessed for energy use. The biomass sources considered are agro-residues, livestock wastes, municipal solid wastes and forest residues. It was discovered that contribution of biomass energy in Nigeria is largely from agro-residues, municipal wastes and livestock wastes while forest residues contribute the least. The energy potential is also expected to continue to grow from about 3.2 E J in 2010 to about 5.5 E J in 2020 and may reach about 29.8 E J in 2050.The estimate compares well with forecasted energy demand and will play a great role in future energy supply. Policy formulations have not favoured the development of biomass technologies for efficient utilization of biomass. There is a need to harness this huge energy potential by employing the various biomass technologies and formulating policies to the effect. Thereis also a need to enhance the development of the agricultural subsector of the economy where the biomass is generated.
A laboratory scale downdraft biomass gasifier was designed to deliver a mechanical power of 4 kW and thermal power of about 15 kW. The gasifier was manufactured as a single piece having a water seal and cover. The gasifier was tested in natural downdraft and forced downdraft mode. Ignition of the fuel beneath the grate, during natural downdraft mode, using wood shavings as fuel, produced gas which burned with a blue flame for 15 minutes. Ignition at the throat, using either palm kernel shells or wood shavings, during the natural downdraft mode, the gasifier did not produce syngas. During the forced downdraft mode, fuel was ignited at the throat. Gasification was successful with the palm kernel shells, during forced downdraft, which produced gas which burned steadily with luminous flame for 15 minutes per kilogram of biomass fed. However, wood shavings experienced some bridging problems during the forced downdraft mode of operation. The fuel conversion rate of the gasifier, when using palm kernel shells as fuel in forced downdraft mode, was 4 kg/h. Forced downdraft mode of operation yielded better results and is the preferred operation of the gasifier.
The study of compaction or solids conveying in a screw extruder has been carried out majorly on the straight screws using the plug flow analysis. Despite this, the analysis of the straight screw appears to be complex as contained in existing literatures based on the force and torque balance. The tapered screw, which is considered to be an effective option for biomass compaction, introduces greater complications because the geometry is constantly changing. In this study, a method based on the traction and retardation mechanism of friction is developed for a fully unwound screw channel utilizing only the force balances. The procedure has been used to carry out a parametric analysis of the tapered screw extruder for a screw press biomass briquetting machine. The taper angle was considered to significantly increase the pressure developed in the extruder depending on the length of the compaction zone. The optimum taper angle has also been found to be dependent on the frictional coefficient of the biomass material with enclosing surfaces and ranges between 2° and 4°. © 2015, Int. Comm. of Agricultural and Biosystems Engineering. All rights reserved.
The contribution deals with the technology of biomass briquetting into the solid high-grade biofuel by screw extrusion machines. It is focused mainly on the theory of compacting tools for screw briquetting presses, their analysis, stress conditions and geometry. The main aim is analyzing of pressing screw geometry and determination process of its design. Analysis of force conditions on the screw is necessary for designed geometry verification and for stress analysis. The determination process of the frictional power is instrumental to main power drive design. Knowledge of these processes is the base of the new tools research for screw presses, the increase of tools lifetime and the competitiveness of whole technology.
The quality of a high-grade solid biofuel depends on many factors, which can be divided
into three main groups — material, technological and structural. The main focus of this paper is on
observing the influence of structural parameters in the biomass densification process. The main goal is
to model various options for the geometry of the pressing chamber and the influence of these structural
parameters on the quality of the briquettes. We will provide a mathematical description of the whole
physical process of densifying a particular material and extruding it through a cylindrical chamber and
through a conical chamber. We have used basic mathematical models to represent the pressure process
based on the geometry of the chamber. In this paper we try to find the optimized parameters for the
geometry of the chamber in order to achieve high briquette quality with minimal energy input.
All these mathematical models allow us to optimize the energy input of the process, to control
the final quality of the briquettes and to reduce wear to the chamber. The practical results show
that reducing the diameter and the length of the chamber, and the angle of the cone, has a strong
influence on the compaction process and, consequently, on the quality of the briquettes. The geometric
shape of the chamber also has significant influence on its wear. We will try to offer a more precise
explanation of the connections between structural parameters, geometrical shapes and the pressing
process. The theory described here can help us to understand the whole process and influence every
structural parameter in it.
The contribution deals with the compacting of material, mainly biomass, which one of the way how to treat the biomass waste. The aim of this contribution is to present how important are structural parameters of briquetting machine pressing chamber at compacting process. The contribution is focused on influencing parameters which is possible to control by structural changes on tools of production machine -briquetting machine. Information which you can read in our contribution was obtained from analyses, experiment and experience with compacting. There is also described influence of some structural parameters on the quality of pressing. Key words: biomass, compacting, briquette density, length and conicalness of pressing chamber, mathematical model of compacting
The goal of this contribution is to present the process of engineering design of briquetting machine pressing chamber. Presented construction of briquetting machine is not the new construction principle of briquetting machine. It's a design of experimental pressing stand. This equipment has one big advantage, provides the possibility to research the impact of structural and technological parameters changes. Authors in this contribution describing the lonely process of briquetting machine pressing chamber design. Described design comes from the basic input requirements and analysis of mathematical models related with process of biomass compacting and related with pressing conditions in briquetting chamber during biomass compacting. In this design are also included requirements resulting from designed experimental plan, that's mean requirements regarding research of impact of structural and technological parameters changes on final briquettes quality. Engineering design is also completed by stress analysis, thus by outputs of FEM analysis of designed pressing chamber construction. 1. I Biomass presents huge amounts of unutilized waste. Solid biofuels production is convenient way how to energetically recover the waste. Before the waste becomes biofuel it has to be modified. Very interesting possibility is to compact the modified waste into the solid high-grade biofuels. This can be performed by compacting technologies, e.g. briquetting or pelleting. The final products of briquetting and pelleting are briquettes and pellets with various shapes and sizes. The feature of these both technologies is pressing of material (waste) under high pressure and temperature without any binding material. It is very important to produce briquettes with Standards given quality. Briquettes quality is evaluated mainly by briquette density and bulk density. Other important briquettes quality indicators are mechanical durability, strength and hardness. During the pressing process there are many parameters which influencing the final briquettes quality.
This article presents a theoretical and experimental study on the measurement and prediction of die pressure in the extrusion process of wood-plastic composite (WPC). Die pressure is an important parameter in processing of WPCs as it governs the product strength, quality, and the final output rate, which directly affects the economy of the production. In this research work, a modular die was designed to accommodate for various circular die inserts to produce rod-shaped products having various diameters. Experimentation was carried out to record the pressure for each product. To develop a theoretical formulation for die pressure, two different schemes were considered and modified: non-Newtonian flow and hot extrusion. The comparison of the experimental and theoretical results demonstrated that the experimental values are between the values predicted by the two theoretical schemes. However, it was shown that by applying a correction factor (based on the compaction ratio of die) into the hot extrusion scheme, a theoretical ground can be suggested for pressure prediction in WPC processing. It appeared that the WPC flow in the die resembles more of a plug flow.
Pressure drops for the extrusion of a perfectly plastic material through smoothwalled dies with various reduction ratios and conical entry angles have been calculated by the large deformation elastic–plastic finite element method. They are found to agree well with extrusion pressures obtained from slipline field analyses for plane strain problems, and lie within the limits set by upper- and lower-bound solutions in axisymmetric cases. The results for axisymmetric dies are compared with the die entry pressure drop term in the Benbow– Bridgwater equation, used to describe the flow of pastes in a ram extruder.
Pelletizing as a complicated compaction process is under continuous
improvement. One of the problems - determination of optimal
technological parameters to attain a sufficiently high density of
pellets - is solved in this paper. The statistical model of density
depending on four technological factors is built based on data obtained
through a central composite design. Canonical analysis is used to find
the stationary point, and as the received point is a saddle point, the
optimal setting is determined by means of ridge analysis. Special
attention is paid to the uncertainty associated with the indirect
measurement of the pellet density. Substantial differences in the
density exist between pellets created under the same conditions, and
especially the type-A uncertainty must be taken into consideration
This paper investigates some of the effects of axisymmetric die geometry and flowrate during the isothermal extrusion of solid chocolate. Experimental observations, such as the material exhibiting a yield stress, flowrate independence and irreversible deformation, indicate that solid chocolate can be modelled using a rigid perfect plastic constitutive model (usually applied to the characterisation of metal forming processes). Numerically obtained extrusion pressures for a range of area reductions, using a commercial finite element package (ABAQUS) in combination with a remeshing code, are compared to experimental data to determine the uniaxial yield stress of the material. Analytical approximations are used to verify the numerical results. A study of the material behaviour in the die land, however, shows that the perfect plastic description can be inadequate in predicting extrusion pressures under certain conditions.
The world is currently facing challenges to reduce the dependence on fossil fuels and to achieve a sustainable renewable supply. Renewable energies represent a diversity of energy sources that can help to maintain the equilibrium of different ecosystems. Among the various sources of renewable energy, biomass is finding more uses as it is considered carbon neutral since the carbondioxide released during its use is already part of the carbon cycle (Arias et al., 2008). Increasing the utilization of biomass for energy can help to reduce the negative CO2 impact on the environment and help to meet the targets established in the Kyoto Protocol (UN, 1998). Energy from biomass can be produced from different processes like thermochemical (combustion, gasification, and pyrolysis), biological (anaerobic digestion, fermentation) or chemical (esterification) where direct combustion can provide a direct near-term energy solution (Arias et al., 2008). Some of the inherent problems with raw biomass materials, like low bulk density, high moisture content, hydrophilic nature and low calorific value, limit the ease of use of biomass for energy purposes (Arias et al., 2008). In fact, due to its low energy density compared to fossil fuels, high volumes of biomass will be needed; adding to problems associated with storage, transportation and feed handling at a cogeneration plant. Furthermore, grinding biomass pulverizes, can be very costly and in some cases impractical. All of these drawbacks have given rise to the development of new technologies in order to increase the quality of biomass fuels. The purpose of the work is mainly in four areas 1) Overview of the torrefaction process and to do a literature review on i) Physical properties of torrefied raw material and torrefaction gas composition. 2) Basic principles in design of packed bed i) Equations governing the flow of material in packed bed ii) Equations governing the flow of the gases in packed bed iii) Effect of physical properties of the raw materials on the packed bed design 3) Design of packed bed torrefier of different capacities. 4) Development of an excel sheet for calculation of length and diameter of the packed bed column based on the design considerations.
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