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EVALUATION OF QUARTZ DEPOSIT IN ANGWAN DOKA, KOKONA NASARAWA STATE-NIGERIA FOR PRODUCTION OF DENSE REFRACTORY BRICKS
ABSTRACT
Samples of quartz were sourced from deposit site at AngwanDokaKokonaNasarawa State Nigeria. The samples were beneficiated and crushed to smaller particle sizes ranging from fine, medium to coarse. The samples were prepared by the semi-dry method, with moulding pressure of 300 kN to form brick. After drying at 110oC, the bricks were burnt at 1450oC. The refractory bricks turned brownish in colour with some spot-dot tint colour on their surfaces; the refractory bricks were investigated to determine their chemical and physical properties. X-ray fluorescence analysis result showed SiO2 to be the major oxide at 96.25%. Other oxides present in the quartz sample as impurities were MgO-0.88%, Fe2O3-0.51%, Cr2O30.18%, CaO-0.02%, etc. Al2O3 and TiO2 were not detected, loss on ignition (LOI) was 2.037% and the total sum of impurity contents of 1.713% falls within the tolerable impurities associated to silicates group of refractories. The refractory bricks have an average linear firing expansion value of 2.9% and it is in accordance with (ASTM C179-14 (2014). The apparent porosity value of the brick was 33.1% which is below recommended ASTM value of (17-25%). The bulk density was 1.7 g/cm3; cold crushing strength was 202.56 kg/cm2. Thermal shock resistance showed that 9 heat cycles were required at 900oCbefore destruction. Therefore, it was categorized as having a good thermal shock resistance; this is due to the fact that the 9 heat cycles falls within recommended ranges of 7-12 cycles for silica dense refractory brick. The quartz from AngwanDokaKokonaNasarawa State formed a silica dense refractory brick which is among the medium heat duty group of silicate refractories. The produced refractory bricks can be used in applications such as construction of reheating furnace roofs, regenerator chambers, furnace doors etc. where moderate strength and heat treatments were required
TABLE OF CONTENTS
Title Page——————————————————————————————- i
Declaration—————————————————————————————— ii
Certification—————————————————————————————– iii
Dedication——————————————————————————————- iv
Acknowledgement——————————————————————————— v
Abstract——————————————————————————————— vi
Table of Contents———————————————————————————- vii
List of Tables————————————————————————————— xi
List of Plates—————————————————————————————- xii
List of Appendices——————————————————————————— xiii
Definition of Terms——————————————————————————- xiv
CHAPTER ONE———————————————————————————- 1
1.0 INTRODUCTION———————————————————————– 1
1.1 Background of the Study—————————————————————- 1
1.2 Statement of the Problem—————————————————————- 5
1.3 Aim of the Study————————————————————————– 6
1.4 Objectives of the Study——————————————————————- 6
1.5 Justification of the Study—————————————————————– 6
1.6 Significance of the Study—————————————————————– 7
1.7 Scope of the Study————————————————————————- 7
1.8 Limitation of the Study——————————————————————- 8
CHAPTER TWO———————————————————————————– 9
2.0 LITERATURE REVIEW—————————————————————- 9
2.1 Introduction——————————————————————————— 9
2.2 Refractory Materials———————————————————————– 9
2.3 Classification of Refractory Material—————————————————- 10
2.3.1 Classification based on chemicomineralogy composition—————————– 10
2.3.2 Classification based on method of production—————————————— 12
2.3.3 Classification based on physical form————————————————— 13
2.3.4 Classification based on refractoriness————————————————— 13
2.3.5 Shaped and Unshaped Refractories—————————————————— 15
2.4 Dense and Porous Refractories———————————————————– 15
2.5 Insulating Refractories——————————————————————— 16
2.6 Special Refractories———————————————————————— 16
2.7 Silica Refractories————————————————————————– 16
2.7.1 Application of Silica Refractories——————————————————– 17
2.7.2 Manufacturing of Silica Refractories—————————————————- 19
CHAPTER THREE——————————————————————————— 20
3.0 METHODOLOGY————————————————————————- 20
3.1 Introduction———————————————————————————- 20
3.2 Materials————————————————————————————- 20
3.3 Equipment———————————————————————————– 20
3.4 Experimental Procedure——————————————————————- 21
3.4.1 Beneficiation of Quartz——————————————————————– 21
3.4.2 Sample Description———————————————————————— 22
3.4.3 Chemical Analysis————————————————————————- 26
3.4.4 Particle Size Distribution/Batch Formulation—————————————— 26
3.4.5 Mixing and Bonding———————————————————————– 27
3.4.6 Shaping, Pressing and Moulding——————————————————— 27
3.4.7 Drying—————————————————————————————- 29
3.4.8 Firing—————————————————————————————– 29
3.5 Mechanical, Physical and Microstructural Properties——————————— 29
3.5.1 Linear Drying shrinkage—————————————————————— 30
3.5.2 Firing Expansion/Shrinkage————————————————————– 30
3.5.3 Apparent Porosity————————————————————————– 30
3.5.4 Bulk Density——————————————————————————– 31
3.5.5 Cold Crushing Strength——————————————————————- 32
3.5.6 Thermal Shock Resistance————————————————————— 33
3.4.7 Microstructural Analysis—————————————————————— 33 CHAPTER FOUR———————————————————————————- 36
4.0 RESULTS———————————————————————————– 36
4.1 Chemical Composition——————————————————————– 37
4.2 Linear Drying Shrinkage—————————————————————— 38
4.3 Calculation of Linear Drying Shrinkage———————————————— 38
4.4 Data Obtained from Linear Firing Expansion—————————————— 40
4.5 Calculation of Linear Firing Expansion————————————————- 40
4.6 Produce Dense Refractory Brick——————————————————— 42
4.7 Data Obtained from Apparent Porosity————————————————– 43
4.8 Calculation of Apparent Porosity——————————————————— 43
4.9 Data Obtained from Bulk Density——————————————————– 45
4.10 Calculation of Bulk Density————————————————————— 45
4.11 Data Obtained from Cold Crushing Strength——————————————– 47
4.12 Calculation of Cold Crushing Strength————————————————— 47
4.13 Thermal Shock Resistance—————————————————————– 49
4.14 Microstructural Analysis——————————————————————- 50 CHAPTER FIVE————————————————————————————- 51
5.0 DISCUSSION——————————————————————————- 51
5.1 Chemical Composition——————————————————————— 51
5.2 Linear Drying Shrinkage——————————————————————- 51
5.3 Linear Expansion of the Quartz Samples———————————————— 51
5.4 Surface Appearance of the Brick———————————————————- 52
5.5 Apparent Porosity————————————————————————— 52
5.6 Bulk Density——————————————————————————— 53
5.7 Cold Crushing Strength CCS————————————————————– 53
5.8 Thermal Shock Resistance—————————————————————– 54
5.9 Microstructural Analysis——————————————————————- 54
5.10 Findings————————————————————————————– 55
CHAPTER SIX————————————————————————————– 57
6.0 CONCLUSIONS AND RECOMMENDATIONS———————————— 57
6.1 Conclusions——————————————————————————— 57
6.2 Recommendations————————————————————————– 58
REFERENCES————————————————————————————– 59
APPENDICES————————————————————————————— 64
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
The term “REFRACTORY” means “HARD TO FUSE”. Refractories are therefore the class of materials which withstand high temperatures, resist the action of corrosive liquids and dust laden currents of hot gases that comes in contact with the material (Chesti, 1994). American Society for Testing and Materials (ASTM) defines refractories as inorganic materials, usually nonmetallic that withstand high temperatures (ASTM, 1975). It was further asserted that any material withstanding temperatures above 538oC (1000oF) is considered as refractory. Such materials includes; aluminosilicates, silica, magnesites, chrome, chrome-magnesite, carbon and dolomite refractories. Others include zirconia, carbides, nitrides, silicides, borides and their compounds.
The criterion of ability to withstand exposure to environments above 538oC (1000oF) is the criterion of distinction separating refractories from other ceramics, fibres and coatings applicable only at lower temperatures. Thus, refractory materials are characterized by the ability to withstand not only the heat but also chemical and slag attack, abrasion impact, resist thermal shock and carry sustained structural stresses at high operating temperatures for as long as possible. Refractories belong to the class of ceramic materials which are employed for high temperature applications, usually above 1000oC. Most refractories are made from naturally occurring high melting point oxides of SiO2, Al2O3, MgO, Cr2O3, and ZrO. Refractories are used in almost every industry in which heat is employed such as in metallurgical, chemical, cement, glass and petrochemical industries. They are used for the construction and maintenance of furnaces, kilns, reactors and boilers (Jock et al, 2013). Refractory materials play a very significant role in high temperature environments, especially, in furnace linings and construction and other applications. They have wide applications in ceramics and glass industries, iron and steel plants, foundries, cement factories, petrochemical industries (Esezoboret al., 2015).
Refractory materials have been developed to serve as heat shields in the construction and maintenance of lining of the interior walls of high temperature equipment like furnaces, flues and reactors thereby protecting the equipment shells (usually made of steel and or cast iron) from breakouts and premature failure during process operations. The iron and steel, ceramics and glass, sugar, cement, petroleum and petrochemical are some of the industries where high temperature operations are inevitable. In such industries, operating temperatures are as high as several hundreds to thousands of degrees (Nurudeen, 2010).
In Nigeria, numerous research works by Amudaet al., (2005); Ameh and Obasi, 92009); Mark, (2010); Nurudeen, (2010); Musa, et al., (2012); Jock, et al., (2013) and Apeh, (2014) had been carried out on the characterization of indigenous refractory raw materials for possible production of quality refractory bricks for furnaces, kilns, ovens and lining to replace the high cost of imported bricks (Apehet al., 2010). The results of these numerous researchers have indicated that high quality refractory bricks can be produced domestically.
It is regrettable, that a huge amount of money, about $229 million, is expended annually to import refractory materials into Nigeria (Apeh, 2014). Various researchers Hassan, (2005); Apehet al., (2011) and Nurudeen, (2010) argued that, this huge spending could be avoided if the bricks were produced domestically in Nigeria.
The prime ingredient for silica refractories, sometimes termed acid refractories, is silica. These materials were well known for their high-temperature load-bearing capacity and are commonly used in the arched roofs of steel and glass-making furnaces; for these applications, temperatures as high as several hundreds may be attained. Under these conditions, some small portion of the brick will actually exist as a liquid. The presence of even small concentrations of alumina has an adverse influence on the performance of these refractories. These refractory materials are also resistant to slags that are rich in silica (called acid slags) and are often used as containment vessels for them. On the other hand, they are readily attacked by slags composed of a high proportion of CaO and or MgO (basic slags), and contact with these oxide materials should be avoided (Callister, 2007).
Silica brick is a refractory which is significant from the chemical point of view by its high content of SiO2 (more than 95 %). As a mineral, it is composed of various modifications of SiO2, particularly β-cristobalite and γ- tridymite (Brunk, 2000). Furthermore, it is composed of a low amount of unmodified β-quartz, calcium orthosilicates, and vitreous phase. The usage of refractory materials, usage of silica bricks as well, is influenced by technological development in the industries where these materials are applied. Their constantly increasing technical quality is an accompanying effect referred to as “Hara-kiri effect.” Despite the unavoidable trend of continuous stagnation of the volumes required by industries, new refractory products are being developed, new technologies invented or new raw materials utilized. One of such products is silica material which is still used for its specific properties (Marinelli, 2008).
The use of silica material is quite specific, being implemented mainly in the following areas of application; in coke production, glass industry and metallurgy with completely different utilization. The biggest volumes are utilized in the construction of coke oven batteries, silica is still hardly replaceable in the crowns of glass melting furnaces and it is being used ever more frequently and also for the top parts of hot blast stoves in metallurgy. Even though the application of silica materials in the areas mentioned above is very effective there is still a potential for reaching an even higher level of quality. The success of this material based on SiO2 is determined mainly by its outstanding performance at high temperatures. The melting point of SiO2 is the lowest one in the category of technical oxides (1726oC) which is why firing is the critical part of the manufacturing process (Brunk, 2000).
Despite this fact it is clear that the desired changes of parameters cannot be attained only by making changes in the firing regime. It is essential to attain maximum density at raw conditions and optimal dosage of mineralizers (maintaining thermodynamic properties) in order to have the optimal solution. Among other issues related to the use of silica bricks are adapting the material’s behaviour to various operational conditions and optimizing its properties for the requirements of specific applications. Reaching better chemical (higher SiO2 content and lower content of melting oxides), physical (lower apparent porosity and higher cold crushing strength) and thermodynamic properties (lower speed of creep) is mostly linked with higher thermal conductivity which is not always an advantage especially in glass industry application (Nevrivova et al., 2014).
AngwanDoka is a remote area in Kokona Metropolis. It is located at Agwada junction off KeffiAkwanga road at kilometre 15 away from Nasarawa State University Keffi, see AppendixE for map and coordinate of AngwanDokaKokona, Nasarawa State. Presently the quartz from AngwanDokaKokona deposit in Nasarawa State has not been evaluated for possible use as a refractory material. The miners’ minerals of interest are the precious minerals such as sapphire, tourmaline and aquamarine etc. They consider the quartz as just a vein that would lead them to these precious minerals; therefore to them it has less or no value. This research is however aimed at evaluating the quartz from this deposit for its refractory properties and applications. Thus, this study will strive to evaluate both the physical and chemical properties of quartz from AngwanDokaKokona deposit and to produce dense refractory bricks. The quartz used for this research was obtained primarily from AngwanDokaKokona, Nasarawa State.
1.2 Statement of the Problem
The development of the iron and steel industry via the rehabilitation of various inland rolling mills and the envisaged completion and commissioning of the Ajaokuta Steel Company Limited indicate that there will be a great increase in consumption of refractory materials. Ajaokuta Steel Company Limited is estimated to require 36,000 tonnes of refractory bricks worth over 120 million Naira just for furnace lining purposes (Musa et al., 2012).
In the past few years, there has been an increasing awareness on the scope, and the importance of refractory materials in the industrial development of Nigeria. Research records show that several workers have investigated the suitability of various locally sourced materials for the production of fire-clay refractories from various deposit (Ahmed, 1986; Garkida, 1998; Adekeye, 1999;
Fasubaet al., 2000, Sullayman, 2006; Abdullahi, 2009; Musa et al., 2012; others include;
Lawrence and Ayo, 2012; Obikwelu, 2012; Hassan and Aigbodion, 2014; Chinagoet al., 2015;
Sani, 2016;). However, no records are available that investigate the properties of quartz from AngwanDoka, KokonaNasarawa State and its use in local production of dense refractory bricks despite the availability of the material. It is imperative, therefore, to attempt to produce silica bricks from this locally sourced raw material in order to curb costs that would result from foreign exchange dissipation due to the importation of the refractory bricks.
1.3 Aim of the Study
The aim of the study is to produce dense refractory bricks from quartz deposit, available at AngwanDokaKokonaNasarawa State Nigeria.
1.4 Objectives of the Study
The objectives of the study are to;
- source and collect quartz sample from its place of deposition via mining at AngwanDoka, with the aid of mining tools and beneficiate the samples using physicochemical methods.
- analyze the upgraded sample with X-ray fluorescence (XRF) for determination of its oxide composition.
- produce proportionate aggregates, develop and mould a suitable body composition from the analyte sample, and then dry and fire the bricks to their fusion temperature for densification and sintering.
- determine the mechanical, physical and microstructural properties of the dense
refractory.
1.5 Justification of the Study
Nigeria is endowed with vast reserves of solid minerals, including, but not limited to, precious metals, stones and industrial minerals. The country was a major exporter of tin, columbite and coal in the early 1970s; however, activities in the mining sector stoped considerably when crude oil production began to take the centre stage, and became a major source of foreign exchange for the country (Nigerian Mining Sector, 2012). With the current dwindling of oil prices, the need to diversify the revenue base of the country has become paramount.
Silica refractories are particularly useful in metallic and non-metallic industries, this is due to their rigidity at temperatures above the range of usefulness of ordinary fire-clay refractories and to the fact that they expand slightly when heated instead of shrinking as clay refractories do.
Local production of silica refractory bricks is of vital importance for the sustenance of the Nigerian process industries which at present are in dilapidated condition. Successful completion of this research will lead to increase in local content for the production of refractories and sustenance of Nigerian process industries, thereby leading to diversifying and boosting the economy of Nigeria. So also, it will catalyse local investment in processes using quartz as raw material like; quartz clock, ceramics and glass, glaze, and enamel, production will also increase.
1.6 Significance of the Study
This research makes an attempt to utilize available raw materials for local production of dense silica refractory bricks for application in high temperature equipment (furnaces and kilns) in processing industries such as ceramic and glass, iron and steel etc. The success of this research is expected to further promote our local industries in the production and possible exportation of these bricks.
1.7 Scope of the Study
This research was delimited to the collection of quartz sample from AngwanDoka, KokonaNasarawa State Nigeria using appropriate tools, beneficiate and upgrades the sample; determine the sample oxides composition via (XRF) analysis. Mix proportionate aggregate, mould and press for compaction and finally produce dense refractory bricks from the sample and test the properties of the bricks for relevant refractory applications.
1.8 Limitation
During the cause of the research, the furnace that was available for use can only attain the maximum firing temperature of 1450. It is an electrical fired furnace therefore; it required uninterrupted power supply for maximum efficiency especially when longer soaking time is required. But unfortunately power instability is one of the major setbacks that affect some properties of the bricks.
Other properties test such as refractoriness under load, modulus of rupture and thermal conductivity were not achieved due to unavailability of necessary equipment to carry out the test.
EVALUATION OF QUARTZ DEPOSIT IN ANGWAN DOKA, KOKONA NASARAWA STATE-NIGERIA FOR PRODUCTION OF DENSE REFRACTORY BRICKS
