Countries in the world, including Vietnam, are promoting the countrys development in the fields of economy, services, and also the field of industrialization of the country. To meet the high demands of human beings, to carry out the industrialization and modernization of the country in todays 4.0 era, it is necessary to have a developed refractory industry, because a developed country. most clearly, the cities and rural areas will constantly have the constructions that are: thermal power plant projects, highrise buildings, supermarkets, bridges, and roads. to meet the increasing demand for more and more modern means and human life. Along with it are the metallurgical industry, construction industry ... etc, born and strongly developed, that industries have demand for refractory materials, especially the metallurgical industry and other Industrial furnaces require building materials to withstand high temperatures.Therefore, in the coming years, the refractory industry will thrive, so my group decided to choose the topic of refractory for their group presentation.
Ho Chi Minh City University of Technology and Education FALCULTY OF VEHICLE AND ENERGY ENGINEERING SUBJECT REPORT THERMAL MATERIALS TOPIC: REFRACTORY MATERIALS INSTRUCTOR: COURSE ID: 192THMA221332E STUDENTS NAME: HCMC, 01/12/2020 TABLE OF PREPARATIONS No Name ID Preparations Making powperpoint slides Presentation I, II Making word file Presentation III, IV Feedbacks of lecturer ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… …………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… 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Tensile strength, torsional bending 2.1.3 Thermal conductivity, specific heat, thermal conductivity: a) Thermal conductivity b) Specific heat c) Temperature conductivity d) Conductivity 10 2.2 Using properties of refractory materials .11 2.2.1 Refractoriness 11 2.2.2 Heat resistance 12 2.2.3 Mechanical strength 12 2.2.4 Volumetric stability at high temperatures 13 2.2.5 Slag strength 14 2.2.6 Thermal expansion 14 CHAPTER III: APPLICATION OF REFRACTORY MATERIALS 15 3.1 Refractory materials in industry 15 3.2 The ramming material 16 3.3.Plastic refractories 18 3.4 The casting material 20 CHAPTER IV: REAL SYSTEM OF REFRACTORY MATERIALS 21 4.1 Structure of refractory brick 21 4.2 Applications real system of refractory materials 22 REFERENCES 24 TOPIC: REFRACTORY MATERIALS INTRODUCTION The reason for choosing the topic Countries in the world, including Vietnam, are promoting the country's development in the fields of economy, services, and also the field of industrialization of the country To meet the high demands of human beings, to carry out the industrialization and modernization of the country in today's 4.0 era, it is necessary to have a developed refractory industry, because a developed country most clearly, the cities and rural areas will constantly have the constructions that are: thermal power plant projects, high-rise buildings, supermarkets, bridges, and roads to meet the increasing demand for more and more modern means and human life Along with it are the metallurgical industry, construction industry etc, born and strongly developed, that industries have demand for refractory materials, especially the metallurgical industry and other Industrial furnaces require building materials to withstand high temperatures Therefore, in the coming years, the refractory industry will thrive, so my group decided to choose the topic of refractory for their group presentation Objectives of the study The goal of searching and collecting information on the properties of high-quality refractory materials has contributed to creating a new look for construction works that have been carried out at home and abroad, bringing the values Therefore, in the coming years, the refractory industry will thrive Object and scope of the study Research subjects include refractory materials that contribute to a new appearance for construction works Scope of research on the actual works built at home and abroad Evaluation method To be able to achieve the goals set out above, students perform the following research methods: Methods of gathering information - From there, synthesize scientific and objective factors to give one more number of proposed directions to use research materials Page | TOPIC: REFRACTORY MATERIALS CHAPTER I DEFINITION AND CLASSIFICATION 1.1 Definition of refractory materials Refractory materials are materials that retain their physical and chemical properties up to a temperature of 1580°C or higher Refractory material is a material that withstands temperatures higher than 1000°C for a long time and does not deform under mechanical loads The refractory industry is the manufacture of products used at high temperatures Refractory materials are widely used in industries such as metallurgy, chemicals, thermoelectricity, porcelain, glass, cement production Refractory materials are used to limit the space in which it is carried process technology and reduce the heat loss of the furnace Fi gure 1.1: Industrial boiler [1] Page | TOPIC: REFRACTORY MATERIALS 1.2 Classification of refractory materials Refractory materials are classified according to many different signs: According to the chemical and physical nature of the refractory starting material It is divided into groups: silicon, alumôsilicate, magnesium, forstenite, spinene, dolomium, carbon, zircon and refractory materials from pure oxides According to fire resistance, refractory materials are divided into categories: - Normal refractory type : from 1580 to 1770°C - High fire type: refractory from 1770 to 2000°C - Very high type : fireproof above 2000°C According to the shape and size, including the types: ordinary blocks, metaphysical blocks, large blocks According to the forming method, there are plastic compression products, semi-dry compression, molding products, and melting agents According to the heat processing properties: there are refractory products and unburned type According to porosity, the product is divided into solid, normal and light To select and use refractory bricks correctly and effectively, it is necessary to know the important properties of refractory materials and their conditions of use Page | TOPIC: REFRACTORY MATERIALS CHAPTER II PROPERTIES OF REFRACTORY MATERIALS 2.1 Physical properties of refractory materials 2.1.1 Structural properties of refractory materials: Structural properties of refractory products have a decisive influence on all of its properties In terms of structure, refractory material is a combination and alternating arrangement of three phases: crystal, glass (amorphous) and gas (pore) The chemical and physical nature and quantity of each phase is completely different To study the structural properties of refractory materials, modern physicochemical methods such as thermal analysis, phase analysis and diffusion structure are used, by polarizing microscopy, electron microscopy and lithological analysis method 2.1.2 Density and strength at room temperature: a) Porosity: to distinguish and evaluate porosity in the product, people divide pores into the following groups Figure 2.1: Types of foam holes in refractory products [2] (1) Closed porous hole (2) Open porous hole (3) Channel porous hole Page | TOPIC: REFRACTORY MATERIALS - Closed porous pores, located in the product's heart, not allow liquids and gases to seep through - Open porous pores, located on the surface of the product, are filled with liquid or gas but not allow them to seep through the product - Channel porous hole, which are double-ended holes, allow liquids and gases to pass through the product easily The gas permeability (or liquid) of the product depends mainly on the size and number of the channel pores and on the pressure difference of the gas (or liquid) at both ends Porosity is assessed by one of the following characteristic parameters: Actual density (density ρt) g/cm3 is the mass of cm of material without pores Apparent density (apparent density ρt) g/ cm 3, is the mass of l cm3 of material including the pore The net porosity Wt,% is the ratio of the volume of the pores (both open and closed) to the volume of the material The apparent porosity, or apparent, Wbk,% is the ratio of the volume of the openings filled with water when boiled to the volume of the material The tightness of porosity Wk,% is the difference between actual porosity and apparent porosity: W k =W t −W bk If the material is saturated with water, the apparent porosity is determined by the formula: W bk = a 2−a1 V a 1: Absolute dry sample mass, (g); a 2: The above sample mass is saturated with water, (g); V: Sample volume, cm3 Water absorption is the ratio of the amount of water absorbed to the mass of the dry sample: B= a2 −a1 100 % V Page | TOPIC: REFRACTORY MATERIALS 10 Crom - 2800 2.00 0.35 0.754 0.15 manhede 3000 2.8 -0.98 0.754 0.15 2400 1.535 -0.25 0.89 0.42 3000 3.3 -1.1 0.892 0.42 3000 4.07 -1.1 0.775 0.3 2000 5.7 -1.6 0.96 0.146 2100 5.2 -1.3 0.96 0.146 2000 16.8 -7.3 0.93 0.135 2500 21 -10.5 0.965 0.15 23 0.35 0.8 Forstenit Spinen Cacbitsilic Carbon brick 2.2 Using properties of refractory materials 2.2.1 Refractoriness The fire resistance of the material is its ability to resist deformation when the part is working at high temperature Fire resistance is one of the basic properties to determine the usability of refractory materials, depending on the chemical composition of the material Table 2.2 Temperature classification of some refractory materials [6] Type of material Refractoriness oC Type of material Refractoriness oC Dinat 1710-1720 Manhedi >2300 Refractory clay 1580-1750 Crom-Manhedi >2000 Kaolin 1740-1770 Đolomit >2000 Samot 1610-1750 Fosteric 1800-1850 Page | 11 TOPIC: REFRACTORY MATERIALS 2.2.2 Heat resistance Thermal stability is its ability to resist damage under variable temperature conditions The cause of product cracking due to temperature fluctuations is the presence of stress inside the product due to the difference in temperature during heating and cooling In the process of uneven heating in the material, shear stress will appear between the material layers due to uneven thermal expansion When cooled, the surface layer shrinks but inside the temperature is still high, so the refractory material will have tensile stress and cracks appear on the surfaces perpendicular to the cooling surface The ability of the refractory material to resist the stresses that occur within the product; depends on its mechanical properties and elastic properties 2.2.3 Mechanical strength An important property of a refractory is its resistance to the effects of temperature and load simultaneously The mechanical strength is characterized by the strain temperature under a load of 0.2N/mm2, representing the soft space during which the product will plasticize The actual working load is usually much less than the test load (0.2 N/mm2) Deformation temperature under load is a very important criterion of characteristic material for its ability to work under the effect of temperature and load This indicator reflects the ability to use correctly than the fire resistance under specific conditions Table 2.3: Heat resistance of some refractory materials [7] Refractory type of material Heat resistance (calcined at 850 oC) Dinat 1-2 Samot: Small, dense seeds 5-8 Medium grain type 10-15 Page | 12 TOPIC: REFRACTORY MATERIALS Coarse grain type 25-100 Manhede 2-3 Crom – manhede 2-3 Crom – manhede (heat durable) >30 2.2.4 Volumetric stability at high temperatures Refractory materials when used are often subjected to high temperatures and longer than the heating temperature when making them Therefore, when working, there will be changes in phase composition, recrystallization and auxiliary clumping Consequently, the material may shrink or sub-expand; that causes products to irreversibly change their long size At high temperatures, most refractory products will stiffen due to clumping This tightening occurs due to the surface tension of the liquid phase, causing rearrangement and incorporation of particles in the material When maintained for a long time at high temperatures, the crystals grow larger and the product becomes more acidic Secondary shrinkage will cause cracks between the grout and bricks, and lead to lower slag and heat resistance of refractory materials The walls and arches of the kiln will gradually sink and be destroyed 2.2.5 Slag strength In industrial furnaces at high temperatures refractory materials are often exposed to liquid, gaseous and solid environments Liquid medium in contact with bricks such as molten slag, molten metal, liquid glass, ash, slag, molten fuel The detailed destructive gas environment is usually combustion products, gaseous fuels, blast furnace gas, hydrogen gas in coke ovens These gases penetrate deeply into the holes of destructive bricks or lower the durability of them Solid medium reacts to refractory bricks such as ore dust, aggregate dust, solid slag or slag or contact between two refractory materials Slag destroying refractory bricks has two forms: corrosion and erosion Page | 13 TOPIC: REFRACTORY MATERIALS 2.2.6 Thermal expansion: The refractory materials, when heated, often expand, and after cooling they return to their original volume Heat expansion differs from secondary expansion due to the change in phase and structure of the material Stress in a material resulting from rapid heating or cooling; It depends on the thermal expansion The coefficient of thermal expansion of a material is determined by the following criteria: Average coefficient of thermal expansion: a tb = Lt −Lt l ;( ) Lt (t−t ) K Real thermal expansion coefficient: a t= dL L dt Relative coefficient of thermal expansion: a= Lt −Lt 100 % Lt Lt : Sample length at 0°C or at room temperature, unit: m; Lt : Sample length at measuring temperature, unit: m; dL : Length variation with temperature dt CHAPTER III: APPLICATION OF REFRACTORY MATERIALS 3.1 Refractory materials in industry: In industry, refractory materials are often used as construction materials for furnaces, drying oven, industrial furnaces… or used to lining various furnaces in industries such as metallurgy, petrochemical, machinery, ceramics • Effect: to ensure that the high temperature resistance element is not deformed or cracked • Role: plays an important role in the system structure, ensuring technical requirements as well as safety when operating the system Page | 14 TOPIC: REFRACTORY MATERIALS In addition, depending on the needs of use (shape, heat resistance, price, brand, ) one can choose different types of refractory materials to suit the purpose Figure 3.1: Metallurgical furnace [8] In civilian, refractory materials are used to design fire-resistant and heat-resistant equipment Page | 15