Design, Construction And Testing of A Charcoal Fired Crucible Furnace : Current School News

Design, Construction And Testing of A Charcoal Fired Crucible Furnace For Melting of 10kg Of Aluminum

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Design, Construction, And Testing of A Charcoal Fired Crucible Furnace For Melting of 10kg Of Aluminum.

ABSTRACT

This research work presents the design concept, construction, and performance evaluation of a10kg capacity portable crucible furnace which uses charcoal as fuel.

The 10kg crucible furnace was designed, constructed using locally available engineering materials mild steel sheet of 3 mm, mild steel (angle iron) of 5 mm, scrap aluminum, asbestos, clay sand, stainless steel sheet of 2mm, stainless steel pipe of 2 mm and wood charcoal.

An electrical kitchen scale with model Noek5055 and thermocouple with model No Kane-may km 340 were used to measure the fuel consumption and heat generated respectively.

The furnace produced the total heat QT = 67,943.16kJ and supplied the heat required to melt 10 kg of aluminum from room temperature to melting temperature QT = 35,859.13 kJ in a duration of 1hr 33min, the total heat absorbed by the furnace components was QFC = 25,425.44 kJ and the heat transferred to the crucible was QC = 14,118.72 kJ.

The efficiency of the furnace was achieved at 76% dividing heat used by total heat supplied and multiplied by 100. The furnace is suitable for use both in the rural and urban areas for casting of different types of aluminum.

The furnace is environmental friendly without health hazards to the workers and can be moved from one place to another unlike the local one. The results of the test of the furnace performance show that it consumes 3kg of charcoal in 1hr 33mins to melt 10kgof aluminum.

TABLE OF CONTENTS

Page
Title Page —————————————————————————————————- i
Approval Page ———————————————————————————————— iii
Acknowledgements —————————————————————————————— iv
Dedication —————————————————————————————————– v
Declaration ————————————————————————————————— vi
Certification ————————————————————————————————- vii
Table of Contents —— ———————————————————————————– viii
List of Tables———————————————————————————————— xvi
List of Figures———————————————————————————————- xvii
List of plates ———————————————————————————————–xviii
List of Abbreviations————————————————————————————– xix
Abstract —————————————————————————————————- xxii
CHAPTER ONE
1.0 INTRODUCTION————————————————————————————-1
1.1 BACKGROUND OF THE WORK—————————————————————-1
1.2 Statement of Research Problems——————————————————————- 3
1.3 Aim and Objectives————————————————————————————3
1.4 Significance of the Study——————————————————————————3
1.5 Justification of the Work—————————————————————————–4
1.6 Scope of the Work————————————————————————————-4
CHAPTER TWO
2.0 LITERATURE REVIEW—————————————————————————- 5
2.1 Crucible—————————————————————————————————6
2.2 Furnace————————————————————————————————— 7
2.2.1 Types of furnace—————————————————————————————- 7
2.2.2 Classification of furnace——————————————————————————–8
2.2.3 Crucible furnace—————————————————————————————–8
2.3.0 Fuels——————————————————————————————————-9
2.3.1 Types of fuels——————————————————————————————-10
2.4.0 Review of the past work on charcoal————————————————————-10
2.4.1 The charcoal fuel—————————————————————————————11
2.4.2 Types of charcoal————————————————————————————– 11
2.4.3 Uses of charcoal—————————————————————————————-11
2.5.0 Aluminum and aluminum alloys—————————————————————— 12
2.5.1 Aluminum———————————————————————————————–13
2.5.2 Cast Aluminum—————————————————————————————–13
2.5.3 Aluminum casting alloy——————————————————————————-13
2.6.0 Mode of Heat Transfer—————————————————————————— 14
2.6.1 Conduction———————————————————————————————-15
2.6.2 Convection———————————————————————————————-17
2.6.3 Radiation————————————————————————————————18
CHAPTER THREE
3.0.0 Material and methodology————————————————————————- 20
3.1.0 Materials and Material selections—————————————————————–20
3.1.1 Materials for the furnace unit————————————————————————-20
3.1.2 Materials for Blower———————————————————————————–21
3.1.3 Material for air pipe———————————————————————————– 21
3.1.4 Material used for insulators————————————————————————– 21
3.1.4.1 Asbestos———————————————————————————————- 21
3.1.4.1a Types of Asbestos———————————————————————————-21
3.1.4.1b Use of Asbestos———————————————————————————— 22
3.1.4.1c Asbestos health hazards————————————————————————— 22
3.1.4.2 Clay sand——————————————————————————————— 22
3.1.4.2 Uses of clay soil————————————————————————————- 23
3.1.5 The charcoal fuel————————————————————————————– 23
3.1.5.1 Calorific value of the charcoal——————————————————————– 23
3.2 Methodology——————————————————————————————- 24
3.2.1 Engineering design———————————————————————————–24
3.2.2 Design consideration———————————————————————————25
3.2.3 General layout of the furnace———————————————————————–25
3.3.0 Design Criteria and theories———————————————————————-25
3.3.1 Determination of the minimum thickness of the furnace wall——————————— 25
3.3.2 Determination of the maximum allowable working pressure for the furnace—————-25
3.3.3 Determination of the stresses set up in the furnace———————————————–26
3.3.4 Determination of the thermal stress set-up in the furnace wall——————————– 26
3.3.5 Investigation of the effect of internal pressure on the furnace dimension——————–26
3.3.6 The change in length of the furnace—————————————————————-26
3.3.7 The change in diameter of the furnace————————————————————-26
3.3.8 Change in volume of the crucible—————————————————————— 27
3.4.0 Combustion chamber——————————————————————————-27
3.4.1 The amount of fuel burnt per hour—————————————————————–27
3.4.2 Determination of the distance between the fire grate and the crucible port——————28
3.4.3 The thermal load of the combustion chamber—————————————————-28
3.4.4 Thermal load of the fire grate———————————————————————- 28
3.4.5 Determination of the design height of the combustion chamber—————————— 28
3.5 Chemical Analysis of the fuel———————————————————————–29
3.5.1 The amount of air required per kg of the fuel for complete combustion——————— 29
3.5.2 Determination of the mass of the products of combustion ————————————-30
3.5.3 Determination of the CO2 content of the flue gas ———————————————–30
3.6 Determination of the required Fan capacity—————————————————- 30
3.6.1 Determination of the power required to drive the fan——————————————-31
3.6.2 Determination of the peripheral discharge velocity——————————————— 31
3.6.3 Determination of the discharge velocity pressure ———————————————–31
3.6.4 Total dynamic head developed by the fan ——————————————————- 31
3.7 Fan Design———————————————————————————————-31
3.7.1 Determination of the fan major diameter——————————————————— 31
3.7.2 Determination of the fan minor diameter ——————————————————– 32
3.7.3 Determination of the fan blade width major —————————————————–32
3.7.4 Determination of the fan blade width minor —————————————————– 32
3.7.5 Determination of the fan blade inlet angle ——————————————————- 32
3.7.6 Determination of the fan casing outlet velocity ————————————————- 32
3.7.7 Determination of the fan casing outlet area ——————————————————32
3.8 Fan casing design calculation———————————————————————– 32
3.8.1 Fan casing inlet area ———————————————————————————32
3.8.2 Determination of the fan casing outlet diameter ————————————————-33
3.8.3 Determination of the fan casing inlet diameter ————————————————– 33
3.8.4 Determination of the fan case width ————————————————————– 33
3.9.0 Belt and pulley ————————————————————————————– 33
3.9.1 Pulley ————————————————————————————————–33
3.9.2 Types of pulley system —————————————————————————– 34
3.9.3 Belt —————————————————————————————————- 34
3.9.4 Uses of belt drive ————————————————————————————35
3.9.5 Types of belts —————————————————————————————- 35
3.9.6 Belt and pulley calculation ————————————————————————-36
3.9.7 Determination of the length of a open belt ——————————————————- 36
3.9.8 Determination of the angle of contact or lap —————————————————- 36
3.9.9 Determination of the velocity ratio of a belt drive ———————————————–36
3.9.10 Determination of the peripheral velocity of the belt on the driving pulley——————37
3.9.11 Determination of the speed ratio —————————————————————– 37
3.9.12 Determination of the house power ————————————————————– 37
3.9.13 Determination of the torque ———————————————————————–37
3.9.14 Determination of the initial tension ————————————————————- 37
3.10.0 Thermal insulators for the furnace————————————————————37
3.10.1 Determination of the effectiveness of insulators ———————————————- 38
3.11.0 Determination of the melting heat————————————————————–39
3.11.1 Determination of the sensible heat of the metal ———————————————– 39
3.11.2 Determination of the enthalpy of fusion ——————————————————– 39
3.11.3 Determination of the superheat value ———————————————————–39
3.11.4 Heat transferred to the wall of the furnace ——————————————————39
3.11.5 Determination of the heat transferred to the crucible furnace ——————————–40
3.11.6 Determination of the total heat absorbed by the furnace components ———————–40
3.11.7 Determination of the total heat required for a melt ——————————————- 40
3.11.8 Determination of the total heat required to be supplied by the furnace ———————41
3.11.9 Determination of the total useful heat ———————————————————–41
3.11.10 Efficiency of the furnace ————————————————————————-41
3.12.0 Determination of the heat losses in the furnace———————————————-41
3.12.1 Loss from the heat carried by dry flue gas ——————————————————41
3.12.2 Loss due to evaporation of hydrogen ————————————————————41
3.12.3 Loss from the evaporation of fuel moisture —————————————————–42
3.12.4 Loss from moisture in the air ——————————————————————— 42
3.12.5 Loss due to unconsumed fuel ———————————————————————42
3.12.6 Radiation loss in the furnace ———————————————————————-42
3.13.0 Performance of the furnace———————————————————————-42
3.13.1 Theoretical thermal efficiency of the furnace ————————————————–42
3.14.0 The energy Balance——————————————————————————–43
3.14.1 Heat balance in the furnace ———————————————————————–43
3.15.0 Design Calculations——————————————————————————–44
3.15.1 Calculation of minimum thickness of the furnace ———————————————44
3.15.2 Calculation of maximum working pressure of the furnace ———————————–44
3.15.3 Calculation of thermal stresses set up in the furnace walls ———————————–45
3.15.4 Calculation of change in the furnace dimension ———————————————–45
3.15.5 Calculation for Combustion chamber ———————————————————– 47
3.15.6 Calculation for the distance between fire grate and the crucible ———————————48
3.15.7 Calculation for the thermal load of the combustion chamber ——————————–48
3.15.8 Calculation for the thermal load of the fire grates ———————————————48
3.15.9 Calculation for the height of the combustion chamber ————————————— 49
3.15.10 Calculation for the amount air required for complete combustion ———————— 49
3.15.11 Calculation for the mass of the products of combustion ————————————49
3.15.12 Determination of the total airflow required in the furnace ———————————50
3.15.13 Calculation of fan air discharge capacity —————————————————– 51
3.15.14 Calculation for the power required to drive the fan —————————————– 51
3.15.15 Calculation of the fan peripheral discharge velocity —————————————- 52
3.15.16 Calculation for the fan discharge velocity pressure —————————————– 52
3.15.17 Total dynamic head developed by the fan —————————————————–52
3.16.1 Calculation for the fan major diameter —————————————————— 52
3.16.2 Calculation for the fan minor diameter ———————————————————-52
3.16.3 Calculation for the fan blade width major —————————————————— 53
3.16.4 Calculation for the fan blade width minor ——————————————————53
3.16.5 Calculation for the fan blade inlet angle ———————————————————53
3.17.1 Calculation for the fan casing outlet velocity ————————————————54
3.17.2 Calculation for the fan casing outlet area ——————————————————- 54
3.17.3 Calculation for the fan casing inlet area ———————————————————54
3.17.4 Calculation for the fan casing outlet diameter ————————————————–54
3.17.5 Calculation for the fan casing inlet diameter ————————————————– -54
3.17.6 Calculation for the fan casing width ————————————————————-55
3.18.1 Calculation for the belt pitch ——————————————————————-55
3.18.2 Calculation for the angle of contact or lap ——————————————————55
3.18.3 Calculation for the velocity ratio of a belt drive ———————————————– 55
3.18.4 Calculation for the speed ratio ——————————————————————–56
3.18.5 Calculation for the initial tension in the belt —————————————————-56
3.18.6 Calculation for the torque transmitted ———————————————————–56
3.19.0 Calculation for the effectiveness of the insulator ——————————————-57
3.20.1 Calculation for the heat required for the melt of aluminum ——————————————-58
3.20.2 Calculation for heat required for melt of kilograms of aluminum —————————61
3.21.0 Calculation for the heat transfer to the furnace ——————————————–63
3.21.1 Calculation for the heat transferred to the crucible ——————————————–64
3.21.2 Total heat absorbed by furnace components ————————————————— 64
3.21.3 Heat for the melt of nkg of aluminum ————————————————————— 64
3.21.4 Total heat supplied by the furnace ————————————————————— 65
3.21.5 Total used heat ————————————————————————————- 65
3.21.6 Number of calories needed for the melt ———————————————————65
3.21.7 Number of grams needed to give number calories of energy ——————————– 65
3.22.1 Heat supplied to the furnace by fuel ———————————————————-65
3.22.2 Heat output of the furnace ————————————————————————-66
3.23.0 Calculation of heat losses————————————————————————-66
3.23.1 Calculation for the loss of heat carried by dry flue gas —————————————-66
3.23.2 Calculation for loss of heat from evaporation of fuel moisture ——————————66
3.23.3 Calculation for loss of heat due to moisture in the air —————————————- 66
3.23.4 Calculation for loss of heat due to unconsumed fuel ——————————————67
3.23.5 Radiation heat loss in the furnace —————————————————————-67
3.23.6 Calculation for the uncounted heat loss ———————————————————67
3.23.7 Calculation for the furnace efficiency ———————————————————–68
3.24.0 Construction —————————————————————————————–70
3.25.0 Fabrication process———————————————————————————–7
3.26.0 Components assembling process—————————————————————-78
3.27.0 Comparison of the designed crucible furnace and conventional type———————–81
3.28.0 Testing of the furnace and operating procedure ————————————————82
3.28.1 Measurements of kilograms and temperature ————————————————– 82
3.28.2 The charcoal fuel ———————————————————————————- 82
3.28.3 Scrap aluminum ———————————————————————————— 82
3.28.4 Temperature Measurements ——————————————————————–82
3.29.0 Experimental procedure ————————————————————————-83
3.29.1 The environment ————————————————————————————83
3.29.2 Sequence of the testing process ——————————————————————-84
3.29.3 Starting the furnace———————————————————————————84
3.29.4 Furnace on testing ———————————————————————————-85
3.30.0 The amount of heat generated———————————————————————85
3.31.0 The amount of fuel used ————————————————————————– 85
3.32.0 Duration for complete melting of aluminum ————————————————— 86
3.33.0 Cost Analysis—————————————————————————————-87
CHAPTER FOUR
4.1.0 Experimental Results ——————————————————————————–88
CHAPTER FIVE
5.0 Discussion of results————————————————————————————94
5.1 No-load ————————————————————————————————94
5.2 With load test ——————————————————————————————-94
5.3 Continuous test method ——————————————————————————- 94
CHAPTER SIX
6.0 Conclusion——————————————————————————————— 98
6.1 Recommendations———————————————————————————— 99
6.2 References——————————————————————————————– 100

INTRODUCTION

It is clear that despite the advances in the mode of melting metal scrap (aluminum), the charcoal-fired crucible furnace is commonly used in Nigeria due to the fact that it can easily be operated, is available all over the country and its construction materials are readily available.

The charcoal fuel used is readily available in all parts of the country. In any foundry, large or small, heat is required to melt different metals and alloys for casting.

This has resulted in the utilization of many types of melting furnaces for ferrous and non-ferrous metals and an alloys furnace is a device in which the chemical energy of a fuel or electrical energy is converted into heat which is then used to raise the temperatures of materials.

Furnaces operating at low temperatures are often called ovens depending on their purposes and there are other furnaces used at higher temperatures for various materials and purposes.

(Folayan, 2001). Furnaces are refractory lined vessels that contain the material to be melted and provide the energy to melt it. Modern furnace types include electric arc furnaces (EAF), induction furnaces,cupolas, reverbetory, and crucible furnaces.

The furnace choice is dependent on the materials and quantities processed. For ferrous materials, EAFs, cupolas and induction furnaces are commonly used. Reverberatory and crucible furnaces are common for aluminum castings. (Beeley,2001).

A crucible furnace is among the oldest and simplest furnaces used in the foundry; it is primarily used to melt smaller amounts of nonferrous metals but can also be used for ferrous metals.

It is mostly used in small foundries or for specialty alloy lines. The crucible or refractory container is heated in a furnace, typically fired with natural gas or liquid propane, although coke, charcoal,oil, or electricity can be used. (www.industrialmetalcasting.com)A crucible furnace is a type of furnace which uses the crucible as a metal container for melting purposes.

The crucible is made from the material of higher refractory properties with higher melting temperature than the materials being melted and it is normally made from clay. Metals are cast into shapes by melting them, pouring the molten metal into a mold, and removing the molded material or casting after the metal has solidified and cooled.

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CSN Team.

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