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Table of Content
Page No
Acknowledgement IIAbstract III
1.0 Introduction 1
2.0 Design and Construction Details of biomass briquetting system 2
2.1 Assemble drawing of briquetting machine 3a. Briquetting machine run by electric motorb. Briquetting machine run by diesel enginec. Briquetting machine run by electric motor with pre heater arrangementd. Briquetting machine run by diesel engine with pre heater arrangement
2.2 Design details and drawings of both the systems (electric and diesel) 5 2.2.1 Feed Screw 5
2.2.2 Screw Housing 62.2.3 Bearing House 62.2.4 Die/ Barrel 72.2.5 Die heater 82.2.6 Main Pulley 92.2.7 Main Power transmission shaft 112.2.8 Pre heater 112.2.9 Hopper 122.2.10 Frame 13
3.0 Briquetting Stoves 15 3.1 Stove-1 16 3.2 Stove-2 17
4.0 Experimental results 19
4.0 Conclusion 22
5.0 References 23
6.0 Appendix 24
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Acknowledgement
We are grateful and like to thank the authority of Swedish InternationalDevelopment cooperation Agency (SIDA) for giving the financial support in doingthe research in BIT Khulna. Thanks are also extended for Prof. S. C. Bhattacharyaand Dr. S. Kumar of Energy field of study under School of EnvironmentResources and Development (SERD), AIT, Thailand for their wholeheartedsupport and cooperation in all sorts of work related to research activities. We aregrateful to the authority of Grameen Shakti (GS) for their kind cooperation toconduct this work. We are also thankful to BIT Khulna, Bangladesh authority fortheir support to perform the work there.
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Abstract
The design, construction and operation details of improved biomass briquettingsystem are presented in this manual. Here three system (Packages) have beenpresented. Packages 1 & 2 are based on research works performed in BIT Khulna,Bangladesh and package 3 is presented based on the work in IoE, Vietnam.
The performance of the stoves in terms of cooking efficiency is also presented.The improved biomass briquetting system can be used for commercial purposewith the raw materials of rice husks, rice straw, wheat husks, saw dust, nut shelland also with mixtures of any two or three raw materials. The production rate forboth the cases is more than 80kg/hr, which is economically beneficial.
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1.0 Introduction
The use of biomass as an alternative energy source would reduce the dependenceon fossil fuels. Country like Bangladesh has large quantities of agricultural andforestry residues, e.g. rice husk, rice straw, saw dust, bagasse, coconut shell,peanut shell, etc. Traditionally, a part of residues is put to various non-energyusage as roofing material, cattle feed, raw materials for paper mills etc. A part ofthe residues is also used for energy production, while the remainder finds nopractical use and wasted. The residues found in variety of forms have highmoisture content and low bulk density. As a result a low heat release per unitvolume and hence high transportation and storage costs when used in natural form.So utilization of these residues as fuel in its original form is often not feasible. Theprocess of densifying biomass shows promise of providing a dry uniform easilystored and conveniently shipped fuel from the wide variety of residues produced inagriculture, forestry and food processing. Therefor the development of simple andeffective design of briquetting system for agricultural wastes and residues wouldbe of much importance.
Briquettes are the modern development of biomass fuel. So traditional stoves arenot efficient enough to burn it properly. Therefore, while introducing briquettingtechnology in a country, it would be important to introduce clean and efficientbriquette stoves as well in order to avoid promotion of efficient briquette stovesproduced bylocal artisans.
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2.0 Design and Construction of briquetting system
On the basis of experimental results the following two system (Packages) weresuggested for the commercial use. The work was done in BIT Khulna, Bangladeshand all the machine components were fabricated locally in Bangladesh.
Package 1. (1) Briquetting machine run by diesel engine (2) Die will be heated by briquetting burning die heater (3) Single hole briquetting stove for domestic use for single family (RETs BIT M-1) (4) Double hole briquetting stove for commercial use or abig size family and for tea stall and hotels (RETs BIT M-2) (5) Smoke removal system to be incorporated (Chimney type)
Package 2. (1) Briquetting machine run by electric power (2) Die will be heated by briquetting burning die heater (3) Single hole briquetting stove for domestic use for single family (RETs BIT M-1) (4) Double hole briquetting stove for commercial use or abig size family and for tea stall and hotels (RETs BIT M-2) (5) Smoke removal system to be incorporated (Chimney type)
On the basis of the work in IoE, Vietnam one more package of briquetting systemis suggestedPackage 3. (1) Without gear box (2) Vietnam screw and die (3) Smoke removal system to be incorporated (Chimney type)
A complete briquetting system is divided into two major components viz.:1 Briquetting machine: To produce briquette.2. Briquette burning stove: Proper burning of briquette for producing heat
and efficient cooking.
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2.0 (a) Briquetting Machine
The screw press type briquetting machine consists of fuel feeding system(hopper), feed screw, power transmission system, die or barrel and a die heater.Pre-heater (raw materials) and smoke removal system is incorporated to the systemto improve the efficiency and environmental conditions.Within the framework of this research two different types of power input weretested. There are:1. Electric power input &2. Diesel power inputA lot of options for the pitch of feeding screw and die heaters were tested andfinally the following were suggested for the packages mentioned above. Detailswill be discussed later. The distinguishable feature of electric and diesel system isthe source of power. In electric system electric motor is driving the screw where asdiesel engine is used for the same purpose in diesel system. Fig.1 shows thecomplete briquetting system run by the power developed by diesel engine and fig.2shows the complete system run by the electric power input.
2.1 Design details of briquetting machine
Table-1: Specification of electric motor and diesel engineElectric power input Diesel systemParticulars
1 2 1 2Rated power, HP 20 15 27 20Rated speed, RPM 1470 1450 2200 2200Net weight, Kg. 132 112 220 180Voltage, V 440 440Current, I 32.3 20.2
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Fig.1: Assemble drawing of briquetting machine run by diesel engineFig.2: Assemble drawing of briquetting machine run by electric motor
Diesel Engine
1 Hopper2 Diesel engine3 Engine wheel4 Engine pulley5 Main pulley6 Bearing house7 Pre heater outer cylinder8 Pre heater inner cylinder9 Die heater exhaust pipe10 Die heater upper portion11 Die heater12 Briquette13 Die14 Screw15 Screw housing
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2.2 Design details and drawings of both the system (electric anddiesel)It is mentioned earlier that, power input all other components of both the systemsare same.
2.2.1 Feed screw:
Table-2: Specification of feed screwParticulars ParticularsLength of screw 490 mm. Lower end diameter 25 mm.Pitch 37.1 mm. Upper end diameter 35 mm.Taper angle 2.32o Initial life 2 hrs.
Fig.3 shows the details of the feed screw.The screw was made by applying various machining process in the localworkshop.The screw conveys the raw material and feed it through the barrel or die of thebriquetting machine. The screw creates pressure on the raw materials when itpasses through die. High temperature and pressure densified the raw material andthe briquette is produced. Finally it performs two main works, one is conveyingand other is densifing the raw materials.
Fig-3: Feed screw (all dimensions are in mm)
Figure-1: Assembly drawing of briquetting machine run byelectric motor
495373.5
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2.2.2 Screw housing:
Screw housing is made by casting and finished by machining. The fuel-feedinghopper is placed above it by using nut and bolt. It is a confined chamber. Rawmaterials enter the chamber through the hopper and are being compressed by thescrew within it. It consists of two parts and is fastened tighter by nut and bolt.
Fig-4: Screw housing (all dimension are in mm.)
2.2.3 Bearing housing:
It is made by using the process of casting. It covers the bearing used in briquettingmachine and protects from dust and other impurities. Bearing having number of1162 and 1163, whose specifications are given below are generally used inBangladeshi briquetting machine.
270
49 37
141
80
20 29225
29
82
18.
15.5
7
Fig-5: Bearing housing
2.2.4 Die/Barrel:
It plays a very important role in briquette machining. It is made by casting. It lookslike a tapered pipe. The screw stands inside the die. The die clearance and the taperangle determine the performance of production rate of briquetting machine. A lotof options have been tested and finally the following was found to be best suitedfor the machine.Die clearance: 45 mm.Taper angle: 1.55o
260
30.06
130
234140 D
50 D
215
8
290
57.6
162.6 D
96.7D
Fig-6: Die (all dimensions are in mm.)
2.2.5 Die heater:
Different types of die heater are used for heating the die. The few heaters are (alltested in Briquetting laboratory, BIT Khulna, Bangladesh)
(1) Electric coil type which are commercially available(2) Briquetting burning die heater made by mild steel(3) kerosene stove and(4) briquetting burning stove made by brick
But briquetting-burning dieheater made by mild steel or of brick is mosteconomical for commercial use.The die heater is used for heating the die. The heat produced in the die, softens thelignin of the raw material and used as a binder. Except electric coil and kerosenestove all die heater exhaust can be used for preheating of the raw materials. It wasfound during experiments that a temperature range of about 200 oC to 250 oC isrequired to soften the waste biomass for segregation of lignin. To maintain suchtemperature inside the die the outer temperature should not be less than 400 oC,which is produced by the die heater. Finally the briquette burning die heater(Fig.7) made of mild steel (MS) sheet is selected for the project. Its cost of energyconsumption is very much comparable with others, shown in table below.
9
228.6355.6
165.1
596.9
76.2
88.9
101.6 D
Fuel
Air supply
Fig-7: Die heater (all dimension are in mm)
2.2.6 Main pulley:
It is fabricated by casting (fig.7). It is circular in shape. The operations of facing,turning, boring, groove cutting (V-type) are performed step by step. Lathe andShaper are used for doing other operations.It is the power transmission device, which transfer power from the motor to themain power transmission of the briquetting machine. Belt is used for transmissionpower from electric motor to the main shaft. RPM of the motor is also reducing byusing pulley of different diameter. RPM of about 400 is suitable for the machine.
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Fig-8: Main Pulley
13050
30
70
30
14
30
M10
130 D
70 D
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2.2.7 Power transmission shaft:
Mild steel is use for making the main power transmission shaft. It is round inshape of length 45 cm and the diameter of 7 cm. All operations for making thisshaft are done by lathe drilling and shaper machine. Its one end joined with themain pulley and other end coupling with screw by a square hole.The main power transmission shaft transfer power from the source (electricalmotor) through pulley to the screw of the briquetting machine. This main shaftrotates with the main pulley. Two bearing are used for decrease the frictional lossof the main shaft.
2.2.8 Pre heater:
The pre heater is made by using MS sheet. Pre heater consists of inner and outercylinder. Inner cylinder is connected to the hopper, which is used to convey theraw material from hopper to screw housing and outer cylinder is used to flow theexhaust from die heater.Pre heater is used to pre heat the raw materials. So that the moisture of the rawmaterials are removed. Here in the laboratory tests it was found that the rawmaterials (rice husk) get heated to about 110 oC. Pre heater of this type savesenergy and increased production rate at the same time reduced environmentalhazards.
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Fig-10: Cross Sectional View of Inner and Outer Pipe ( All dimensions in mm.)
2.2.9 Hopper:
The hopper is made by the sheet metal. Different size and shape of hopper is usedfor the briquetting machine.Raw materials are stored in the hopper when the machine runs. Waste biomass(husk) is feed gradually to the machine and briquette is produced. Fig. 11 showsthe details of the hopper used in the Bangladeshi machine.
1601580
1596 150
280D
400 D110
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Fig-11: Hopper
2.2.10 Frame:
Frame is made by different size of angle bar and sheet metal. In the figure below acomplete frame is shown.The function of the frame is to hold the motor. It also resists vibration duringrunning. Fig. 11shows details of a typical frame.
520
80
260
150
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Fig-12: Frame (All dimensions in mm.) 450450
450
670666
180
180
7.76
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3.0 Briquetting stoves:
Five different types of Briquetting stoves have been developed, fabricated andtasted in the Briquetting laboratory, BIT Khulna. Out of which one has beenselected for commercial use and one has been suggested for domestic use. Thetwo-hole type briquette burning stove is suitable for hotel, tea stall, small messes,or for a big size family and single hole portable one is suitable for small sizefamily. Fig.12 and fig.13 show the constructional details and dimensions of doubleand single hole stoves respectively.
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3.1 Stove 1: (RETs BIT M-1)
It is a double chamber stove made of mud. The thickness of mud is 10 cm. Onegrate is placed at a depth of 18 cm from the top. Two pots can be used at timefigure shows its construction details. This type of stove is suitable in tea stall,small mess or cooking for a large size family.
330
110
18080
70
220120
200 D
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3.2 Stove 2 (RETs BIT M-2)
It is conical shaped stove. The outer layer is made of MS sheet and a layer of4.5cm mud is put inside. A grate is placed at a depth of 11 cm from the top. Thegrate is made of MS rod having 80% opening for airflow from bottom. Ash isdisposed through the grate time to time. This type of stove is suitable for domesticuse for a small family.
180 D
110110
240
160
670
70
100 25
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4.0 Experimental Results:
Assumptions:Cost analysis for briquetting system1. The machine will run 25 days per month and 10 hours operation
per day2. Husk price is Tk. 0.90 per kg.3. Economic life of screw is 77 hrs.4. Labor charge per hour is Tk.10.005. Sales price of briquette is Tk.2.50 per kg.With this considerations the following results are obtainedA. Electric system (package-2)1. Production cost of briquette = Tk.2.07/kg.2. Pay back period = 0.63 years3. Benefit cost (B/C) ratio = 1.21
B. For diesel system (package-1)1. Production cost of briquette = Tk.1.72/kg.2. Pay back period = 0.33 years3. Benefit cost (B/C) ratio = 1.45
Table-2: Comparative cost and Benefit of Electric and Diesel system
Type of cost Electric system Diesel systemAmount Tk/hr Amount Tk/hr
Fixed cost Machine costLand cost
Installation cost
0.981.00.1
1.131.00.1
Total fixed cost 2.08 2.23
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Variable cost Raw materials cost1.Machine operatingcosta. Cost of die changingb. Cost of screwchangingc. Labor costd. Energy cost
90.00
0.80
17.5310.0063.90
90.00
0.80
17.5310.0031.5
Total Variable cost 182.23 149.83Machine
depreciation cost1.0 1.2
Maintenance cost 1.0 1.5Total cost (90 kg) 186.31 154.76Sales price of 90kg. of briquette Tk.
225.00 225.00
Net profit in onehour
38.69 70.24
Net profit per day 386.9 702.4Net profit per year 116070.00 210720.00Pay back period 0.63 Yr. 0.33 Yr.Benefit cost ratio 1.21 1.45
4.1 Advantage of using preheater:
Table.3: Comparison of using preheater with that of non-preheatersystem:
Flowrate
Kg/hr
Temperature to beraised for rawmaterials (0C)
Productionrate Kg/hr
Powerconsumption
rateKWh/kg
132 125 120 0.126With preheater 116 138 105 0.122
123 250 112 0.146Withoutpre heater 85 250 77 0.145
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Table-4: Test result of different raw materials for briquettingmaking:
Cost of briquetteRawmaterials
Productionrate
Powerconsumptionrate
ElectricsystemTk/kg
DieselSystemTk/kg
Bagasse 55 0.145 2.55 2.19Wheat husk 90 0.135 1.91 1.70Rice straw 52 0.148 2.34 2.07Rice husk 85 0.143 1.78 1.51Saw dust 60 0.158 2.04 1.92
Table-5: Test results for effect of pitch of screw on screw life andproduction cost for both the systems (Electrical and Diesel)
Cost of productionPitch ofscrew
Productionrate Kg/hr.
Averagescrew life Electric
systemTk./Kg
DieselsystemTk/Kg.
5.0 120 7.78 1.8 1.55.0 85 8.42 1.91 1.614.0 110 7.93 1.94 1.564.0 80 8.73 2.08 1.623.8 90 8.27 2.18 1.733.5 66 8.25 2.56 1.82
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4.2 Performance data of briquetting stove:
Table-6: Dimension and performance of btiquetting burning stoves
Stove 1 Stove 2 Stove 3 Stove 4Diameter 26 30 26Thickness of insulation (cm) 10/10 4.5 6 4.5Height of the combustion chamber(cm)
18/18 11.0 12.0 11.0
Grate area (cm2) 360/265 165 150 165Area of air flow through grate(cm2) 40 23 23 23Pot hole diameter(cm) 22/18 15 15 15Efficiency (%) 56.76 31.76 24.61 29.77
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5.0 Conclusion:
1). Briquetting is a site specific and sensitive technology.2). By briquetting system waste biomass is converted to very usefuland acceptable solid fuel.3). The price of briquette is competitive with that of fuel wood.4). Briquetting stove is easy to construct and use at the same timeefficient in comparison to conventional one.5). Income generation may be created through the application of thistechnology.
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6.0 References:
1. Final report, RETs in Asia program, Phase-I, submitted by Prof.Dr. Md. Nawsher Ali Moral to AIT Bangkok, Thailand inDecember 1998.
2. Final report, RETs in Asia program, Phase-II, submitted by Prof.Dr. Md. Nawsher Ali Moral to AIT Bangkok, Thailand inDecember 2001.
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7.0 Appendix
7.1 Some constructional photograph
Biomass Briquetting Laboratory, BIT Khulna, Bangladesh
Diesel Engine operated briquetting machine
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Fig 14 (plate -1): Biomass Briquetting laboratory
Fig. 15 (plate –2): Complete biomass Briquetting system operated by diesel engine
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Fig. 16 (plate –3): Complete biomass Briquetting system operated by electricmotor
Fig. 17 (plate –4): Screw having different pitch and length used in briquettingmachine
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Fig. 18 (Plate – 5): Biomass Briquetting Stove – 1 (RETs BIT M-1)
Fig. 19 (Plate – 6): Construction of chinese stove in training class
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Fig. 20 (plate – 7) National seminar on URERAB-2001 at BIT Khulna on behalf ofthe SIDA project
Fig. (21 (Plate – 8) Resurfacing of the Screw
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7.2 Efficiency test of stove (water boiling method)
The stove efficiency can be calculated by using the following formula
Where,
mw.i = Mass of water initially in cooking vessel, kgCpw = Specific heat of water, kj/kg0Cmw,evp = Mass of water evaporated, Kgmf = mass of fuel burned, kgTe = Temperature of boiling water 0CTi = Initial temperature of water in pot, 0CHl = Laten heat of evaporation at 1000C and 105 pa, KJ/kgHf = Calorific value of fuel, kj/kg
Instrument and Equipment
1. Two aluminium pot without lid2. Temperature sensor for measuring the ambient and boiling water
temperature3. Digital balances for measuring the weight of pot, water and fuel
Procedure
At first both the empty pots were weighted separately and the values recorded Thepots were then partially filled with water and weighted again. The initialtemperature of water was recorded. The briquetting stove was then ignited and thewater in the both pot in case of double holes was left to boil and evaporated. Aftercomplete burning of fuel supplied, both pots were weighted again and the amountsof water evaporated in each pot was recorded.
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Experimental Data and results
Table 8 : Sample calculation for single hole stove (RETs BIT M-1)
Type of fuel Rice husk briquetteWeight of fuel 1.5 kgCalorific value of fuel 15000 kj/kgInitial water temperature 280CBoiling water temperature 980CWeight of pot 0.4 kgWeight of pot + water 3.5 kgFinal weight of pot + water 1.2 kgWeight of water evaporated, pot 2.3 kgLatent heat of water evaporation 2770 kj/kgSpecific heat of water 1 kj/kgEfficiency = 29.28%
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Table 9 : Sample calculation for double hole stove (RETs BIT M-2)
Type of fuel Rice husk briquetteWeight of fuel 1.5 kgCalorific value of fuel 15000 kj/kgInitial water temperature 280CBoiling water temperature 980CWeight of pot 0.4 kgWeight of pot + water 3.4 kgFinal weight of water + pot1 1.6 kgFinal weight of water + pot2 2.7 kgWeight of water evaporated, pot1 1.8 kgWeight of water evaporated, pot2 0.7 kgLatent heat of water evaporation 2770 kj/kgSpecific heat of water 1 kj/kgEfficiency = 32.6%
7.3 Local entrepreneurs/manufacturers for technology transferand extension work:
Some entrepreneurs have been found for producing the briquettingmachine and its spares, one of them is:
Pubali Engineering LimitedMoilapota, KhulnaBangladesh
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Contact Address:
Professor Dr. Md. Nawsher Ali MoralProject Co-ordinatorBiomass Briquetting Project (SIDA)Department of Mechanical EngineeringBIT Khulna, Khulna-9203, BangladeshPhone : +88-041-774065
+88-041-769471 Ext. 401 (0), 402 (R)Fax : +88-041-774403E-mail: [email protected]
Professor S. C. BhattacharyaCoordinatorRenewable Energy Technologies in Asia (RETs in Asia) ProgramEnergy field of studySchool of Environment, Resources and DevelopmentAsian Institute of Technology (AIT)P.O. Box 4, Klong LuangPathum Thani-12120Thailand.Tel ; +662 524 5403
+662 524 5440Fax : +662 524 5439
+662 524 2126Email : [email protected]
Swedish International Development Cooperation AgencyS-10525 Stockholm, Sweden.Tel : +46(0)86985000, Fax : +46(0)8249290Home page : www.sida.se
