iJARS 660 AUTH COPY

International Journal of Applied Research and Studies (iJARS)
ISSN: 2278-9480 Volume 2, Issue 10 (Oct - 2013)
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Manuscript Id: iJARS/660 1|
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Research Article
Design and Fabrication of Biomass Briquetting Machine
Authors:
1
Jadhav O. K. *, 2
Dhakne K. A.
Address For correspondence:
1, 2
Pune Vidyarthi Griha’s College of Engineering and Technology, University of Pune, India
Abstract- Biomass briquettes are a bio fuel substitute to coal and
charcoal. They are used to heat industrial boilers in order to produce
electricity from steam. The most common use of the briquettes are in
the developing world, where energy sources are not as widely
available. There has been a move to the use of briquettes in the
developed world through the use of cofiring, when the briquettes are
combined with coal in order to create the heat supplied to the boiler.
This reduces carbon dioxide emissions by partially replacing coal
used in power plants with materials that are already contained in the
carbon cycle. Manufacturers mainly use three methods to create the
briquettes, each depending on the way the biomass is dried out.
Although biomass briquettes are usually manufactured, biomass has
been used throughout history all over the world from simply starting
campfires to the mass generation of electricity. 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
Keywords: Screw extrusion, Screw briquetting machine, highgrade
biofuel, screw presses
1. INTRODUCTION
Biomass is renewable source of energy, potentially
sustainable and environmentally benign. They are the derived from
living plants, animal manures, waste products from the processing
industries and other sources. They substitute for fossil fuel as energy
(non-renewable) source resulting in a net reduction in greenhouse gas
emissions. World production of biomass is estimated at around 146
billion metric ton per year .Huge volumes of agricultural residues and
wood processing residues are not fully utilized. One of the major
world crop, rice, has about 25% of the crop in the form of husk,
which amounts to about 100 million tonnes of residues. On a small
scale, world production of groundnut is about 10 million tonnes of
which about 45% is shell. Although there are crops with both high
and low residue yields, it is reasonable to assume that about 25% of
any dry agricultural feedstock is residue. Field residues are the major
biomass, which could be utilized as feedstock for production of
briquettes, ethanol and gaseous fuels. For example, high yielding
maize can produce field residues as much as 11 t/ha annually; a more
likely yield in most developing countries would be 25 t/ha, with rice
being the highest yielder. Cotton crop produces 4 to 20 t~a annually.
Process residues such as bagasse from sugarcane, coffee husks,
groundnut shells, rice husk, coir dust, saw dust, furniture wastes, etc.
Can also be briquetted. Biomass has huge quantities of energy, which
are derived during the process of photosynthesis. This renewable
form of energy can be recovered by combustion process or by
conversion of biomass into usable form such as ethanol,
pellets/briquettes, bio-oils or producer gases. The net energy
available from biomass ranges from 20 MJ/kg for dry plant matter to
55 MJ/kg for methane, as compared to coal with about 27 MJ/kg
.Biomass have low bulk density. This causes major problem during
storage, handling and transportation for further processing. The
lowest bulk densities are around 40 kg/m 3 for loose straw and
bagasse; the highest levels are around 250 kg/m 3 for some wood
residues. Thus, gain in bulk densities of 2 to 10 times can be expected
from densification. Direct burning of unprocessed biomass for
industrial applications is very inefficient. One of the strategies to
overcome this is to densify them into pellets or briquettes, which also
increases the volumetric energy content, reduces transportation cost
and makes it available for a variety of applications .Densification
involves the use of some form of mechanical pressure to reduce the
volume of biological matter, which is easier to handle and store than
the original material. Densification ofbiomass is mostly called
briquetting, when it is utilized for energy production. Densification of
biomass for animal feed production is called pelleting and cubing.
2. DESIGN OF SCREW BY REVERSE ENGINEERING
The screw briquetting process consits of extrusion of the
material by a screw extruder which acts as a continuous feeder. The
volume of the material is decreased as it is transferred from the
hopper to the die exit. This is achieved by increasing the root
diameter of the threaded shaft gradually starting with a small
diameter at the feeding position and increase gradually to a maximum
value at the die position. Figure 4 shows the design of the screw. Due
to the limited manufacturing facilities at the location of the plant the
screw manufacturing was the biggest challenge faced during the
process. Making the extruder screw was really a big challenge when
dealing with such a task in an environment of limited manufacturing
facilities.
The easiest method was found is to taper the shaft diameter from one
side into a conical shape and then grooving the thread base on the
shaft tapered surface, then welding a heavy steel plate to form the
thread. The thread height was made constant and of a value
okj099@gmail.com *Corresponding Author Email-Id

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smaller by only a little clearance than the inner diameter of
the barrel, this was conducted using a normal lathe turning operation.
The feed stock consists of the slurry mixture of the carbonized
powdered cotton stalks and the binder. The briquettes were relatively
moist when produced and required to be placed under the sun for
drying before packing them for distribution.
Figure 1: Graph showing counter pressure (vs) length of the
briquette
2.1 Analysis of Vietnamese screw for reverse engineering.
Vietnamese briquetting machine consists of following
Specifications.
1. A briquetting machine of Vietnamese design with gearbox for
power transmission, a 15 HP electric motor, and a Vietnamese screw
and die pairfor producing 71 mm diameter briquettes,
2. A coal/briquette-fired die-heaterstove, and
3. A smoke removal system (chimney type)
2.2 General specifications of screw
Motor: 15 hp; 1450 rpm 220/380V; 50 Hz
Total length: 340 mm
Length of threaded portion: 212 mm
Screw speed: 200-240 rpm Weight: 3 kg
Die-heater: 10.6 kW coal stove; can also use biomass briquettes.
Outer diameter of screw: 70 mm
No. of screw thread: 4.5
Material: Mild Steel rod – 35 mm dia.
Production rate: 75-90 kg/h Mild steel washer: 4 mm thick
Raw materials: Ricehusk, coffee husk, saw dust
Die
Electricity consumption: 0.12 kWh/kg
No. of grooves: 8
Width: 500 mm
Length: 250 mm
Tapered length: 75
Power transmission: Gear Box
Internal dia - Front: 71 mm; Rear: 78 mm
Weight: 400 kg
External dia - Front: 80 mm; Rear: 92 mm
Don’t exist many publications which described
mathematical models including impact of individual structural
parameters. We did some analyses and we found two mathematical
models which contains also structural parameters. Therefore we were
able to test them a check their impact on other parameters in these
models. The first mathematical model represents following equation
PG = PK e (4λµH) /D
k .........................................................................(1)
Closer describing of the model you can find on Figure. This
mathematical model is describing compacting process on vertical
press and is describing effecting forces and pressures in the pressing
chamber. We tried to test the impact of length of compacted briquette
H. From this result we will be able in future calculate the optimal
length of pressing chamber. By testing we chose unit values for other
parameters in model and step by step we raise the value of length of
compacted briquette always about 10%. The results you can see in
following. On the base of single-axis pressing theory in closed
chamber we can analyze impact of length of pressing chamber
change. Diameter of pressing chamber with length of pressing
chamber has significant impact on briquette properties at burning and
also on pressing tool wearing. By burning of briquettes is needed
slow combustion. This we can execute when the surface/volume ratio
of briquettes is the smallest as can be. The same situation is also by
pressing tools wearing. The pressing tool wearing is smaller when
smaller surface/volume ratio of pressing tools is. Therefore is very
significant to find the optimal geometry of pressing chamber
according to briquettes burning, to tools wearing and according to
trade requests. Pressing conditions in closed chamber at single-axis
pressing when is the counter pressure generated by counter pressure
plug is shown in Figure 2. Maximal compacting pressure PK which is
rising by pressing depend on pressing chamber length and shape;
depend on friction relations between compacted material and wall of
the chamber.
Drag friction is backward assigned by radial pressure PR, applied to
chamber wall, by friction coefficient μ, and length of compacted
briquette H.
[Pm - (Pm + dPm)](πDk
2
/4)-µPRπDkdx = 0 .......................................(2)
And
Pk = Pg e (4λµH) /D
k .............................................................................(3)
Specifies relation between axial pressure pk and counter pressure
effecting on compacted briquette pG. This mathematical model was
designed by German researchers [1]. This mathematical model allows
us to calculate the suitable length of compacted briquette, suitable
counter pressure and suitable length of pressing chamber. With
combination of friction coefficient and length of pressing chamber we
can provide needed counter pressure at compacting. But how impact
the length of pressing chamber and counter pressure the final
briquette quality represents by briquette density? Answer to this
question can give us only the mathematical model which specifies
relation between axial compacting pressure and briquette density.
Therefore we designed the experiment for main influencing
technological and material parameters evaluation. We tried to find
functional dependence
ρ = f (p, T, wr, L) …...........................................................................(4)

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where: ρ – briquette density (kg.dm-3), p – axial compacting pressure
(MPa), T – pressing temperature (ºC), wr – relative material moisture
(%) and L – fraction largeness (mm). We designed experimental
pressing stand (see Figure) on which were executed experiment. This
experimental stand allowed us to change the values of mentioned
parameters and helped obtained suitable results for mathematical
model designing.
Figure 2: Graph showing briquette density (vs) compacting pressure
2.3 Development of Experimental Setup
1. Screw development :
Basis of design : Estimation and assumptions
a. Final briquette density was 1000kg/m3
, while at the inlet
of hopper the bulk density of saw dust was about
250kg/m3,
accordingly the compression was assumed to
be 4 times and the initial pitch of thread, shank diametre
was decided.
b. Compression was to be achieved in several stages,
broadly compression in screw and maximum of
compression in tapered barrel, accordingly the pitch and
the numbers of turns over the screw were fixed.
c. Screw has a entirely new design. All the avalaible
litreature regarding the screw design was just a
prerequisite.
d. Unlike the existing design of Vietnamese screw analysed
by reverse engineering , this screw has a varying pitch
with straight shank and straight outer diametre.
e. For cost cutting, screw was first turned on lathe with a
straight shank and then later washers were welded over it
to form the helix rather than machining the entire as a
single component.
2. Bearing selection:
a. Depending on the screw shank the bearing was selected.
Bearing with housing with internal diametre 22 was
selected and then the required load calculations were
done.
b. TYPE: a. Deep groove ball bearing
b.Thrust bearing
3. Development of straight and tapered barrel:
After the screw and bearing design was completed, the outer
barrel was designed. Keeping a minimum clearance between the
outer diametre of screw and barrel surface the internal and outer
diametres were fixed, also the length of barrel was fixed arbritarily.
4. Other avalaible components include Motor (1.44 Hp, 1440 rpm),
gearbox (reduction 1:30), a 3ph electric supply.
3. ANALYSIS
As the major and the critical component of the machine i.e
the screw was developed by reverse engineering, analysis on any
software was not done. The prototype was directly built up and tested
for vibration ana;ysis, failure portions.
The following were the results observed after the trial run.
1. Initial washer thickness was 2 mm, due to very large
pressure(130 Mpa) that was created the washers were
crushed under stress.
2. The base structure was not rigid and the torque imparted to
the entire machine created a toppling effect over the entire
assembly.
3. The material chosen by us was saw dust (bulk density
being 250 kg/m3
), however required compression ratio
was not achieved.
4. The process required the need of a suitable binder in saw
dust, the given sample of saw dust was tested for briquette
formation on a standard coal briquetting machine but the
efforts were in vain, the material in its original form did not
form briquettes.
5. Most of the compression was expected in the tapered
portion of the barrel, however material failed to transfer
from the last screw thread into the tapering portion.
6. The motor power was insufficient (1.44 Hp).
3.1 Dealing with the problems
1. Washer thickness was increased from 2mm to 4mm .
2. Dead weight was added on to the base structure making it
more rigid.
3. Material was kept the same and machine oil was added to it.
4. Motor kept the same the number of revolutions were
changed (increased).
5. The taper angle was changed from 150
to 80
.
4. FINAL MACHINE SPECIFICATIONS AND
ANALYSIS
1. Motor: 1.44 Hp; 1440 rpm 220V; 50 Hz
2. Total length of screw: 282 mm
3. Length of threaded portion: 152 mm
4. Screw speed: 50-55 rpm Weight: 1.8 kg
5. Outer diameter of screw: 52 mm
6. No. of screw thread: 6.5
7. Pitch reduction as- 30(2x)-27-24-21-18-16 (all in mm.
in 6.5 turns)
8. Material: Mild Steel rod – 54mm dia.
9. Mild steel washer: 4 mm thick
4.1 Cad drawings of actual fabricated components

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Figure 3: Screw shank
Figure 4: Washer
Figure 5: Washers welded over the shank

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4.2 Some actual photographs to support the drawings.
Photograph 1: Screw
Photograph 2: Assembly
Photograph 3: Washer
Photograph 4: Actual Briquette formed
Photograph 5: Briquette
5.RESULTS AND DISCUSSION
Thus analysis using software was not done here. The
already existing Vietnamese screw was studied and the model was
scaled down with a suitable factor. The photographs are clicked when
the actual components were being fabricated. Entire process was
based on trial and error. The dimensions were chosen of the
components based on a safety factor and accordingly whatever
changes had to be made after the trial run were made. Though by
reverse engineering the varying pitch of the screw improved the
compression ratio and achieved the expected results in just a power of
1.44 Hp where on the other hand the conventional machines use 18-
22 Hp. The screw can be termed as ‘conveying cum compression
screw with a varying pitch’. If mass production is adopted of such
smaller capacity machines, then these machines would be very
cheaply available to the masses. The agrarian class can be benefited
by this to a greater extent. A lot of waste is generated from
agricultural activities, this waste can be effectively used in the
briquetting machines to generate briquettes, sold at the rate of Rs 30-
40 per kg. It can be called as the best that is done out of waste. This
would not only benefit the farmers economically but also serve as a
purpose to dispose off the degradable waste.

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6. CONCLUSION
The use of biomass briquettes is strongly encouraged by
issuing carbon credits. One carbon credit is equal to one free ton of
carbon dioxide to be emitted into the atmosphere. India has started to
replace charcoal with biomass briquettes in regards to boiler fuel,
especially in the southern parts of the country because the biomass
briquettes can be created domestically, depending on the availability of
land. Therefore, constantly rising fuel prices will be less influential in an
economy if sources of fuel can be easily produced domestically. Lehra
Fuel Tech Pvt Ltd is approved by Indian Renewable Energy
Development Agency (IREDA), is one of the largest briquetting
machine manufacturers from Ludhiana, India. In East Africa, work on
biomass briquette production has been spearheaded by a number of
NGOs with GVEP( Global Village Energy Partnership) taking a lead in
promoting briquette products and briquette entrepreneurs in the three
East African countries namely Kenya, Uganda, and Tanzania. This has
been achieved by a five year EU and Dutch government sponsored
project called DEEP EA (Developing Energy Enterprises Project East
Africa. The main feed stock for briquettes in the East African region has
mainly been charcoal dust although alternative like sawdust, bagasse,
coffee husks and rice husks have also been used. These briquettes find a
wide use in gasifiers ( as a replacement to diesel), have a wide demand
in hotels for heating purposes in ovens . A commercial approach is aslo
profitable if undertaken this on a large scale. This machine was
particularly developed by us keeping in mind the material to be used
(saw dust). If parametrs like :
1. Compression ratio
2. Bulk density of material
3. Avalaibility of biomass
4. Calorific value
Are altered and studied then even an universal machine
can be developed which could handle varioyus types of homogeneous
mixtrures and not specifically be binded to a single
REFERENCES
1. Tabil, L.G. Jr. and S. Sokhansanj (1996), "Compression and
Compaction Behavior of Alfalfa Grinds, Part 1" Compression
Behavior", Powder Handling and Processing, 8(1), pp. 17-23.
2. HORRIGHS, W., Determining the dimensions of extrusion
presses with parallel-wall die channel for The compaction and
conveying of bulk solids,
Aufbereitungs – Technik: Magazine, Duisburg,
Germany, 1985, No.12.
3. ASAE 368.4 (2006). Compression Test of Food Materials of
Convex Shape. St. Joseph, MI (USA): American Society of
Agricultural and Biological Engineers (ASABE).
4. Eriksson, S. & Prior, M. (1990). The Briquetting of Agricultural
Wastes for Fuel. Rome: Food and Agriculture Organization of
the United Nations, Publications Division.
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