TOPIC 02_Portland Cement, Ceramics, and Glass Industries PDF

PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department CHE 0317-1 – Chemical Process Industries Portland Cement, Ceramic, and Glass Industries (Written Report) Submitted by: Atrero, Garbriel Oliver M. Dormindo, John Paul D. Eugenio, Niel Benson S. Estares, Jeffrey L. Lim, Ryan James B. Submitted to: Engr. Carlos Miguel C. Dacaimat September 16, 2024 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Table of Contents Cement Industry........................................................................................ 4 Introduction............................................................................................. 4 Brief History of Calcareous Cements...................................................... 4 Types of Cement...................................................................................... 5 Manufacturing Companies...................................................................... 8 Portland Cement..................................................................................... 9 Chemical Composition........................................................................... 9 Product Uses........................................................................................ 10 Raw Materials...................................................................................... 11 Block Flow Diagram and Process Flow Diagram...................................... 13 Detailed Manufacturing Process............................................................ 15 Lime and Gypsum.................................................................................. 19 Product Composition............................................................................ 19 Product Uses........................................................................................ 19 Raw Materials...................................................................................... 20 Block Flow Diagram and Process Flow Diagram...................................... 21 Detailed Manufacturing Process............................................................ 23 Ceramic Industry...................................................................................... 27 Introduction........................................................................................... 27 Brief History of Ceramics...................................................................... 27 Types of Ceramics................................................................................. 29 Manufacturing Companies.................................................................... 32 Clay....................................................................................................... 32 Product Composition............................................................................ 32 Product Uses...................................................................................... 33 Page | 2 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Raw Materials...................................................................................... 33 Block Flow Diagram and Process Flow Diagram...................................... 34 Detailed Manufacturing Process............................................................ 35 Ceramic Magnets (Ferrites)................................................................... 38 Product Composition............................................................................ 38 Product Uses........................................................................................ 39 Raw Materials...................................................................................... 42 Block Flow Diagram and Process Flow Diagram...................................... 43 Detailed Manufacturing Process............................................................ 44 Glass Industry.......................................................................................... 50 Introduction........................................................................................... 50 Brief History of Glass............................................................................. 50 Types of Glass....................................................................................... 51 Manufacturing Companies.................................................................... 52 Glass..................................................................................................... 53 Properties of Glass............................................................................. 53 Composition of Glass......................................................................... 53 Raw Materials...................................................................................... 55 Block Flow Diagram and Process Flow Diagram...................................... 56 Detailed Manufacturing Process............................................................ 58 References............................................................................................... 64 Page | 3 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Cement Industry Introduction Cements are defined to be as adhesive substances that can unite masses of solid matter into a compact whole. Cements contain compounds of lime as its principal constituent; when they are mixed with water, they form a paste that subsequently sets and hardens. The term ‘cements’ in this restricted sense is then equivalent to ‘calcareous cements.’ The characteristic feature of cements is useful especially for solid and rigid structures required to be formed and hardened immediately. Figure 1 Cement for Concrete and Masonry Construction Brief History of Calcareous Cements The history of calcareous cement has reflected different moods of economic buoyancy. There have been periods of growth and periods of recession. In modern times no other material has had so great an influence upon the construction world. In fact, no other building material has made a lasting impression on the public as cement-based structures. With that, the following time periods shortly describe the development of cements from prehistoric times up until the modern times. Prehistoric and Ancient Times: Early civilizations such as those of Egypt and Mesopotamia used construction methods that did not involve cement, relying on mud, bitumen, or unbaked bricks. Egyptians later developed a form of mortar from gypsum for building the Great Pyramids, although lime cement was introduced only during Roman times. Greek and Roman Innovations: The Greeks and Romans pioneered the use of volcanic deposits (e.g., Santorin earth) mixed with lime and sand to create durable, water-resistant Page | 4 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department mortar. Romans also utilized powdered tiles or pottery as an alternative when volcanic material was unavailable. The term "cement" originated from these materials. Middle Ages: After the fall of the Roman Empire, mortar quality declined, but the term "cement" continued to be used for various types of binding materials, as seen in medieval texts. 18th and 19th Centuries: In 1796, James Parker patented "Roman cement," which was quick-setting and useful for hydraulic work. However, it was replaced by Joseph Aspdin's invention of Portland cement in 1824, which was named after its resemblance to Portland stone and became the foundation for modern cement. 1914: The first cement plant in the Philippines was established by the Ynchausti business in Binangonan, Rizal. However, the factory soon shut down due to challenges making cement of a consistent grade. 1969: Thirteen cement plants were established, producing an estimated value of 85 million bags annually. 2024: The Philippine Cement Industry has faced challenges because of the after-effects of the COVID-19 pandemic. These challenges include increasing imports mostly from Vietnam, cement dumping from other countries, and struggling demand. Because of this, local manufacturers have been forced to downscale operations which worsens the state of the market. To address these threats, ‘Buy Local, Build Lokal’ program is promoted by government agencies, namely, the Cement Manufacturers Association of the Philippines and Department of Trade and Industry. Types of Cement Cements have various types, depending on its properties, structure, and materials of construction. According to Shreves (1984), Portland cement has five types. 1. Portland Cement American Society for Testing and Materials (ASTM Standard C 219-94) defines this product as a hydraulic cement produced by pulverizing Portland-cement clinker, and usually containing calcium sulfate. In the Unites States, five types of Portland cement are recognized which are listed below. a. Type I. Regular Portland Cement – These are used for concrete construction. This product as its own types, such as white (contains less ferric oxide), oil-well cement, and quick-setting cement. b. Type II. Moderate-heat-of-hardening Portland cement – These cements are used when moderate heat of hydration is required and/or for general concrete construction when exposed to moderate sulfate activity. The heat evolved from these cements should not exceed 295 and 335 J/g after 7 to 28 days, respectively. c. Type III. High-early-strength (HES) cement – These cements are made from raw materials with a lime-to-silica ratio higher than that of Type I cement and are also ground finer than said cements. In other words, they have higher concentrations of tricalcium Page | 5 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department silicate in comparison to regular Portland cements. Because of this along with finer grinding, hardening and heat evolution are faster. d. Type IV. Low-heat Portland cement – These cements possess a lower percentage of tricalcium silicate and tricalcium aluminate. Instead, these cements contain a higher percentage of tetracalcium aluminoferrite and dicalcium silicate. As a result, heat evolution is lower. The heat evolved should not exceed 250 and 295 J/g after 7 and 28 days, respectively, and is 15% to 35% less than the heat of hydration of regular or HES cements. e. Type V. Sulfate-resisting Portland cement – These cements resist sulfates better than the other four types because of their composition or product processing. This is used when high sulfate resistance is required, that is, it contains lower concentrations of tricalcium aluminate than regular cements. Instead, it possesses higher content of tetracalcium aluminoferrite. 2. Portland Pozzolana Cement (PPC) This cement is not cementitious alone; it becomes so when mixed with lime. The natural pozzolans are volcanic tuffs while the artificial one is made from burnt clays and shales. Portland Pozzolana Cement is made by mixing Type I Portland cement with pozzolanic materials like fly ash, volcanic ash, or silica fumes. The pozzolanic materials contain high amounts of silica which reacts with the calcium hydroxide to form calcium silicate hydrate. PPC is used extensively in general construction projects because it improves durability and resistance to chemical attack (especially sulfate and chloride resistance). It is widely used in marine structures, hydraulic structures, and for mass concreting where heat of hydration needs to be controlled. 3. Calcium Aluminate Cement This cement is regarded as high-alumina cement. Calcium aluminate cement contains high proportions of calcium aluminates (typically CA, C₁₂A₇, and CA₂ phases). The key reactive components include alumina and lime. It is characterized by a very rapid rate of development of strength and superior resistance to sea water and sulfate-bearing water. Calcium aluminate cement is used where rapid strength gain is required (e.g., in emergency repair works or refractory applications). It is also preferred in environments with exposure to sulfate, chloride, or acid attacks due to its chemical resistance 4. Special or Corrosion-Resisting Cements These cements are designed to withstand chemical attacks that ordinary Portland cement cannot resist. They often include modifications: a) low in tricalcium aluminate which reduces the formation of expansive compounds like ettringite that cause cracking in sulfate- rich environments; b) higher levels of alumina, making it resistant to acidic environments; and Page | 6 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department c) incorporation of ground granulated blast furnace slag (GGBFS), improving sulfate and chloride resistance. Moreover, these are used in large quantities for chemical equipment such as brick-lined reactors, storage tanks, absorption towers, fume ducts and stacks, pickling tanks, floors, sumps, trenches, and. acid digesters. Figure 2 Product Types for Cements: a) Portland Cement, b) Regular Portland Cement, c) Moderate-Heat- of-Hardening Portland Cement, d) HES Cement, e) Low-Heat Portland Cement, f) Portland Pozzolana Cement, g) Calcium Aluminate Cement, h) Special Cements (a) (b) (c) (d) (e) (f) (g) (h) Page | 7 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Manufacturing Companies The Philippine Cement and Concrete Industry contributes significantly to the Philippine economy by at least 1% of the GDP, in which it generates an estimated 130,000 direct and indirect jobs. In addition, the local industry helps in improving the country’s health and safety industrial standards, environmental stewardship, and is a participant in the country’s strengthening circular economy. According to 6Wresearch, the market is expected to grow at a CAGR of 5.6% from 2020 to 2026, mainly due to increasing infrastructure initiatives sponsored by the government and rising residential construction projects. With that, the top cement companies based in the Philippines are all listed in Table 1. Table 1 Cement and Concrete Companies in the Philippines. Company Name Location Eagle Cement Corporation San Ildefonso, Bulacan Republic Cement & Building Materials, Inc. Norzagaray, Bulacan; Teresa, Rizal; Taysan, Batangas; Danao City, Cebu; and Iligan City, Lanao del Norte Holcim Philippines Inc. Bacnotan, La Union; Norzagaray, Bulacan; Lugait, Misamis Oriental; and Iligan City, Lanao del Norte CEMEX Holdings Philippines Inc. Naga City, Cebu and Antipolo City, Rizal Northern Cement Corporation Sison, Pangasinan In 2023, Portland cement has achieved a volume of 2.3 billion tons globally. The manufacturing companies for the said cement now focuses on increasing production efficiency while reducing environmental impacts. Like the initiatives of the Philippine government, different countries are developing their own new infrastructure projects, including the development of public housing and roads, which drives the market to grow. The market volume is estimated to reach 3.1 billion tons by 2032, having a CAGR of 3.2% from 2024 to 2032. With that, some of the top Portland cement manufacturers internationally are listed below. Page | 8 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Table 2 Top Portland Cement Companies Worldwide Company Name Location Mitsubishi Cement Corporation California, United States Alamo Cement Company Texas, United States UltraTech Cement Limited Maharashtra, India; Chhattisgarh, India; Gujarat, India; Andhra Pradesh, India NCCL, India; Orissa, India Tamil Nadu, India; West Bengal, India; Gujarat, India Heidelberg Cement Limited (Italcementi) Mitchell, Indiana; Gorazdze, Poland; Lengfurt, Germany; Mainz, Germany; Ennigerloh, Germany; Ait Baha, Morocco; Damoh, India; Yerraguntla, India; Sitapuram, India; Ammasandra, India; Jhansi, India; Sholapur, India; Chennai, India; and Cochin, India Anhui Conch Cement Corporation Limited Anhui Province, China; Andijan State, Uzbekistan; Tashkent Province, Uzbekistan; Hongkong, Hongkong; Luang Prabang, Laos; North Sulawesi; Indonesia; Banten, Indonesia; South Kalimantan, Indonesia; and Qashqadaryo, Uzbekistan Portland Cement Portland cement is the most common type of cement used in construction and is the primary ingredient in concrete. It is a finely ground powder made by heating a mixture of limestone (calcium carbonate) and other materials (such as clay) to high temperatures in a kiln, then grinding the resultant clinker into a fine powder. The name "Portland" comes from its resemblance to Portland stone, a type of building stone quarried in England. Chemical Composition There are four compounds considered as major constituents of cement which are listed in Table 3. The raw materials used in manufacturing Portland cement consists mainly of lime, silica, alumina, and iron oxide. These compounds interact with one another to form a series of more complex products until a state of chemical equilibrium is reached. However, equilibrium is not maintained during cooling; the rate of cooling influences the crystallization degree and the amount of amorphous material (i.e., glass) present in the cooled clinker. Nevertheless, cement can be assumed in a state of frozen equilibrium—the cooled products are considered in equilibrium at the Page | 9 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department clinkering temperature. This assumption is used in calculating the compound composition of commercial cements. Table 3 Main Compounds in Portland Cement Name of compound Oxide composition Abbreviation Tricalcium silicate 3𝐶𝑎𝑂. 𝑆𝑖𝑂2 𝐶3 𝑆 Dicalcium silicate 2𝐶𝑎𝑂. 𝑆𝑖𝑂2 𝐶2 𝑆 Tricalcium aluminate 3𝐶𝑎𝑂. 𝐴𝑙2 𝑂3 𝐶3 𝐴 Tetracalcium aluminoferrite 4𝐶𝑎𝑂. 𝐴𝑙2 𝑂3. 𝐹𝑒2 𝑂3 𝐶4 𝐴𝐹 Tricalcium and dicalcium silicates are the most important compounds because they are responsible for the strength of hydrated cement paste. These silicates are present with minor oxides in the solid solution which causes a significant effect on the atomic arrangement and hydraulic properties of the silicates themselves. On the other hand, tricalcium aluminate is undesirable to be present within a cement because it lacks contribution to strengthen the properties of cement at its early formation. If the hardened cement paste is attacked by sulfates, C3A forms to become calcium sulfo-aluminate (ettringite), which may cause disruption to the constitution of the cement. The only benefit of the aluminate is that it facilitates the combination of lime and silica when manufacturing cement. Tetracalcium aluminoferrite is present in small amounts and does not affect the cement’s behavior significantly. If this compound reacts with gypsum, it reacts to form calcium sulfoferrite and this accelerates the hydration of the silicates. In addition to the main compounds listed in Table 3, there are some other compounds present in small quantities, namely: 𝑀𝑔𝑂, 𝑇𝑖𝑂2 , 𝑀𝑛2 𝑂3 , 𝐾2 𝑂 and 𝑁𝑎2 𝑂. The oxides of sodium and potassium are referred to as the alkalis because they react with some aggregates which results in the formation of alkali-aggregate reaction. This disintegrates the concrete and reduces the gain strength of cement. Product Uses Portland cement is the backbone of modern construction and plays a fundamental role in the cement and construction industry due to its versatile properties and wide range of applications. Portland cement is the key ingredient in concrete, which is a mixture of cement, water, sand, and aggregates. Concrete is used for constructing buildings, bridges, highways, dams, and many other structures. Besides concrete, this is a vital component in mortars (used for masonry work) and grouts (used for filling gaps and voids). Page | 10 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department This product is often blended with supplementary cementitious materials (e.g., fly ash, slag, silica fume) to produce blended cements. These blends improve the performance, durability, and sustainability of cement-based products, especially in environments exposed to harsh chemicals or extreme temperatures. This is an energy-intensive and a significant source of CO₂ emissions, mainly due to the decomposition of limestone and the energy required to heat the kiln. As such, the cement industry is working on alternative materials and carbon capture technologies to reduce its environmental footprint. Raw Materials Portland cement is prepared through mixing of materials containing calcium carbonate and clay in proper ratios. According to Bogue (1947), the specifications for the production of Portland Cement in the United States in 1942 and 1944 are as follows: limestone, cement rock, clay and shale, gypsum, blast-furnace slag, sand and sandstone, marl, and iron materials. Figure 3 Raw Materials Used for Portland Cement: a) Limestone, b) Cement Rock, c) Clay, d) Shale, e) Gypsum, f) Blast-furnace Slag, g) Sand and Sandstone, h) Marl, i) Iron Materials (a) (b) (c) (d) (e) (f) (g) (h) Page | 11 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department (i) 1. Limestone Limestone is the primary component in producing Portland cement as it contains calcium carbonate (see Figure 3a). When this material is heated in a kiln for a cement manufacturing process, it undergoes calcination. Calcium carbonate then decomposes into calcium oxide and carbon dioxide. The process is given below ℎ𝑒𝑎𝑡 𝐶𝑎𝐶𝑂3 → 𝐶𝑎𝑂 + 𝐶𝑂2 In addition, when the calcium oxide reacts with other raw materials containing silica, alumina, and iron oxide, they form the four main compounds found in cement (known collectively as clinker). To reiterate, these compounds are responsible for the strength development of cement. 2. Cement Rock Cement rocks are naturally occurring sedimentary rocks that possess a mixture of calcium carbonate, silica, alumina, and iron oxides. It may be considered as a blend of limestone and clay (see Figure 3b). 3. Clay and Shale This contains silica, alumina, and iron oxide, contributing to the cement’s strength and its properties. Some natural sources of these materials include glacial lakes and shale bedrock. Figure 3c and 3d show both raw materials. 4. Gypsum As seen in Figure 3e, gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (𝐶𝑎𝑆𝑂4 ⋅ 2𝐻2 𝑂). This material is added in the final grinding stage of clinker to regulate the setting time of the cement. Gypsum acts as a cement retarding agent as it will prevent the premature hardening of the cement, especially after its mixing with water. On the contrary, if gypsum is not added in the process, the cement would “flash set”, that is, it would harden immediately when mixed with water. This results in poor construction properties of the cement. Page | 12 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department 5. Blast-Furnace Slag A blast-furnace slag (see Figure 3f) is a by-product from the iron-making process in which molten iron is separated from impurities in a blast furnace. It contains mainly of silicates and aluminosilicates of calcium and other bases. Because of this, blast-furnace slag may be used as supplementary cementitious material (SCM) to reduce the amount of clinker required and lower carbon emissions. This material possesses latent hydraulic properties—in the presence of an activator (e.g., calcium hydroxide), it will react with water to form the main constituents found in Portland cement. In effect, it aids in the strength development of the main product. Some primary sources of blast-furnace slag include iron ore, coke, and flux. 6. Sand and Sandstone Figure 3g shows the material, and it is primarily composed of silicon dioxide in the form of quartz. Sand and sandstone are the source of silica for the formation of the silicate phases in clinker, particularly C3S and C2S. These two are often mixed with limestone and other raw material which are heated in the kiln so the silica will react with the calcium oxide to form the silicate phases. 7. Marl Figure 3h shows marl which is a sedimentary rock containing mixtures of clay and calcium carbonate. It may also be considered as a natural blend of limestone and clay. Because of this, it may be used as a single raw material as a source of calcium carbonate and silica for clinker production. This reduces the amount of limestone and clay or shale in the processing. Marl rocks are found near bodies of water since very fine-grained clay particles are deposited in such locations under water, which then compacts by overlying sediment. 8. Iron Materials Figure 3i shows an iron ore. Iron materials (e.g., iron ore, mill scale, or iron oxides) are natural sources for the formation of C4AF. Although it contributes less to the strength of the final Porland cement product compared to the calcium silicates, C4AF acts as a fluxing agent in which it reduces the melting temperature in the kiln, allowing the clinker to form at lower temperatures. As a result, lower energy consumption is achieved. In addition, C4AF helps the cement resist chemical attacks. Block Flow Diagram and Process Flow Diagram Manufacturing Portland cement is a complex process. This can be divided into three sections: raw materials preparation, clinker calcination, and cement grinding. Figure 4 and Figure 5 display both the Block Flow Diagram (BFD) and Process Flow Diagram (PFD) of the manufacturing process, respectively. Page | 13 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 4 Block Flow Diagram of Portland Cement Manufacturing (Golewski, 2020) Figure 5 Process Flow Diagram of Portland Cement Manufacturing (Carpio et al., 2008) Page | 14 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Detailed Manufacturing Process As mentioned previously, the manufacturing process of Portland cement can be divided into three main parts. 1. Preparation of Raw Materials and Handling The acquisition of raw materials is the initial production step. Portland cement plants are generally located near to a calcareous raw material source. Calcium, the element of highest concentration in Portland cement, is gathered from a variety of calcareous raw materials (e.g., limestone, chalk, marl, seashells, etc.). These raw materials are obtained typically from open-face quarries, underground mines, and/or dredging operations, which they all vary from one facility to another. For instance, some quarries have relatively pure limestone while others provide chemical blends already in the limestone. Other important elements, such as silicon, aluminum, and iron, are collected from ores and minerals that are also found within the vicinity of quarries. After the raw materials are quarried, they must undergo the next steps: crushing, blending, grinding, and storage. A variety of blending and sizing operations are designed to obtain appropriate chemical and physical properties before feeding into the rotary kiln. Initially, the raw materials are crushed using a cement crusher (see Figure 6). The type of crusher to be used depends on some factors (i.e., moisture content, hardness, abrasion, mechanical robustness, and operating costs), and the crushing method (i.e., extrusion, cutting, impact). Figure 6 Types of Cement Crushers Page | 15 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department To further pulverize the materials, the grinding mill is used (see Figure 7a). The equipment provides the quality and fineness of the crushed raw materials. The products are then stored in large silos for additional processing. Figure 7 a) Vertical Grinding Mill, and b) Cement Silos (a) (b) 2. Calcination of Clinker Clinker calcination is the most important stage in the entire Portland cement manufacturing process. As a pretreatment for the pyro-processing stage, there are two ways: the dry method, and the wet method. The difference between the two is the form of the kiln feed. The former uses a raw material as a fine powder feed while the latter combines the raw mix with water to create a slurry feed. a. Dry Process – For a dry process kilns, the moisture content of the raw materials are reduced to less than 1%. Drying alone can be done using impact dryers, drum dryers, paddle-equipped rapid dryers, air separators, or autogenous mills. However, the widely used method, and most efficient, is by utilizing hot exit gases from the pyro-processing system. Other sources of thermal energy for drying includes exhaust gases, direct-fired coal, oil, and gas burners. At last, the dry materials are transported in silos using conveying systems (e.g., screw conveyors, belt conveyors, drag conveyors, bucket elevators, etc.). Page | 16 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 8 Drying Equipment for Clinker Calcination: a) Impact Dryers, b) Drum Dryers, c) Paddle-Equipped Rapid Dryers, d) Air Separators, e) Autogenous Mills (a) (b) (c) (d) (e) b. Wet Process – In this process, the raw materials are mixed with water during the grinding process in the mills. This produces a pumpable slurry that contains approximately 65% solids. The slurry is agitated, blended, and stored in various kinds and sizes of cylindrical tanks. After completing the pretreatment, the feed is delivered to the rotary kiln (see Figure 9) to begin the pyro-processing system, which is the heart of the Portland cement manufacturing process. This system converts the raw mix feed into clinkers—these are gray, glass-hard, spherically shaped nodules that range from 0.32 to 5.1 cm in diameter. The rotary kiln is heated at a high temperature so that the constituents of the raw mix chemically react with each other to form such clinker. Page | 17 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 9 Cement Rotary Kiln The transformation to clinkers is quite complex, and it may be seen conceptually into four stages, as a function of location and temperature of the materials within the rotary kiln. Evaporation of uncombined water from raw materials, as material temperature increases to 100°C; Dehydration, as the material temperature increases from 100°C to approximately 430°C to form oxides of silicon, aluminum, and iron; Calcination between 900°C and 982°C while carbon dioxide evolved to form CaO; and Reaction, of the oxides in the burning zone of the rotary kiln, to form cement clinker at temperatures of approximately 1510°C Rotary kilns are elongated, cylindrical furnaces with a slight incline, lined with refractory material to safeguard the steel structure and maintain heat inside. The raw material mixture is fed into the kiln from the higher end, while combustion fuels are typically introduced at the lower end in a counterflow direction. The kiln's rotation gradually moves the materials toward the lower end. As the materials progress through the kiln, they transform into cementitious or hydraulic minerals due to the rising temperatures. Page | 18 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department 3. Blending and Grinding of Finished Portland Cement This is the final step in the process. For this, the clinker will be ground in a grinding mill to achieve the targeted quality or fineness of the cement product. Gypsum, fly ash and other raw materials are added in the grinding process (up to 5% gypsum or natural anhydrite) to improve the blend of the cement, thereby increasing its characteristics. Then, the finish milling is completed almost exclusively in ball or tube mills. At last, the cement is packed properly and sent to the market. Lime and Gypsum Product Composition Lime Lime is sold as a high-calcium quicklime containing not less than 90% of calcium oxide and from 0 to 5% of magnesia with small percentage of calcium carbonate, silica, alumina, and ferric oxide present as impurities. Gypsum usually refers to two kinds of minerals: raw gypsum and anhydrite. Raw Gypsum is calcium sulfate dihydrate ((Ca (SO4) 2H2O), also known as gypsum dihydrate, gypsum or gypsum, composition CaO (32.6%), SO3 (46.5%), H2O+ (20.9%), monoclinic system, crystal is plate-like, usually dense block or fiber, white or gray, red, brown, vitreous or silky luster, Mohs hardness is 2, density 2.3g/cm3. Anhydrite is anhydrous calcium sulfate (Ca (SO4)), theoretical component CaO (41.2%), SO3 (58.8%), orthorhombic system, crystal is plate, usually dense block or granular, white, grayish white, vitreous luster, Morse hardness is 3 – 3.5, density 2.8~3.0g/cm3. Product Uses Lime Lime itself may be used for medicinal purposes, insecticides, plant and animal food, gas absorption, precipitation, dehydration, and causticizing. It is employed as a reagent in the sulfite process for papermaking, dehairing hides, recovering by-product ammonia, manufacturing of high-grade steel and cement; water softening, manufacturing of soap, rubber, varnish, refractories, and sand-lime brick. Lime is indispensable for mortar and plaster use and serves as a basic raw I material for calcium salts and for improving the quality of certain soils. Page | 19 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Gypsum Gypsum is a widely used industrial material and building material. Building Gypsum: Mostly used in building mold ash, painting, masonry mortar and all kinds of gypsum products. Model Gypsum: less impurities, white color, mainly used for ceramic culture process, a small amount for decorative relief. Floor Gypsum: Mainly used for demanding mold ash engineering, decorative products and plasterboard. Whitewash Gypsum: Made of cementing material with appropriate amount of retarder, water- retaining agent and other chemical admixtures. Gypsum can also be used in the manufacture of cement, sulfuric acid, soil improvers, food coagulants, pesticide diluents as well as medical and cosmetology. Raw Materials Lime The carbonates of calcium or magnesium are obtained from naturally occurring deposits of limestone, marble, chalk, or dolomite. For chemical usage, a rather pure limestone is preferred as a starting material because of the high-calcium lime that results. The quarries furnish a rock that contains as impurities low percentages of silica, clay, or iron. Such impurities are important because the lime may react with the silica and alumina to give calcium silicates or calcium alumino-silicates which possess not undesirable hydraulic properties. Gypsum The raw material of gypsum powder is natural gypsum ore. Gypsum is a widely distributed mineral, which is mainly formed by sedimentation and weathering, and a few are found in hydrothermal sulphide deposits. Gypsum usually can be found in the form of crystals or deposits beds. Gypsum formed in sea basins and lake basins is formed by evaporation of brine or hydration of anhydrite; symbiosis with anhydrite, gypsum, etc. It is layered or lenticular in the interlayer of limestone, red shale, marl and sandy clay. The gypsum in the oxidation zone of sulfide deposits is mainly caused by sulfides. Page | 20 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Block Flow Diagram and Process Flow Diagram Figure 10 Lime Processing Block Flow Diagram Page | 21 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 11 Lime Processing Process Flow Diagram Figure 12 Gypsum & Lime Processing Block Flow Diagram Page | 22 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 13 Gypsum Processing Process Flow Diagram Detailed Manufacturing Process Lime The basic processes in the production of lime are: (1) quarrying raw limestone; (2) preparing limestone for the kilns by crushing and sizing; (3) calcining limestone; (4) processing the lime further by hydrating; and (5) miscellaneous transfer, storage, and handling operations. The heart of a lime plant is the kiln. The prevalent type of kiln is the rotary kiln, accounting for about 90 percent of all lime production in the United States. This kiln is a long, cylindrical, slightly inclined, refractory-lined furnace, through which the limestone and hot combustion gases pass countercurrently. Coal, oil, and natural gas may all be fired in rotary kilns. Product coolers and kiln feed preheaters of various types are commonly used to recover heat from the hot lime product and hot exhaust gases, respectively. Page | 23 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department The next most common type of kiln in the United States is the vertical, or shaft, kiln. This kiln can be described as an upright heavy steel cylinder lined with refractory material. The limestone is charged at the top and is calcined as it descends slowly to discharge at the bottom of the kiln. A primary advantage of vertical kilns over rotary kilns is higher average fuel efficiency. The primary disadvantages of vertical kilns are their relatively low production rates and the fact that coal cannot be used without degrading the quality of the lime produced. There have been few recent vertical kiln installations in the United States because of high product quality requirements. Figure 14 Vertical Kiln During the calcining the volume contracts and during the hydrating it swells. For calcination the average fuel ratios are, using bituminous coal: 3.23 lb. of lime from 1 lb. of coal in shaft kilns and 3.37 lb. in rotary kilns. The calcination reaction is reversible. Below 650°C, the equilibrium decomposition pressure of CO2 is quite small. Between 650 and 900, the decomposition pressure increases rapidly and reaches 1 atm at about 900°C. In most operating kilns the partial pressure of CO2 in the gases in direct contact with the outside of the lumps is less than 1 atm.; therefore, initial decomposition may take place at temperatures somewhat less than 900°C. The decomposition temperature at the center of the lump probably is well above 900°C., since there the partial pressure of the CO2 not only is equal or near to the total pressure but also must be high enough to cause the gas to move out of the lump where; it can pass into the gas stream. The total heat required for calcining may be divided into two parts: sensible heat to raise the rock to decomposition temperature and latent heat of dissociation, theoretical heat requirements per ton of lime produced, if the rock is heated only to a calcining temperature of 900°C." are approximately 1,300,000 B.t.u. for sensible heat and 2,600,000 B.t.u. for latent heat. Actual calcining operations because of practical considerations, e.g., lump size, time, require that the rock Page | 24 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department be heated to between 1200 and 1300oe., thereby increasing sensible heat requirements by some 350,000 B.t.u. per ton of lime produced. Then theoretical heat requirements will be approximately 4,250,000 B.t.u. per ton of lime produced. About 40 percent is sensible heat; the rest is latent heat of decomposition. About 15 percent of all lime produced is converted to hydrated (slaked) lime. There are 2 kinds of hydrators: atmospheric and pressure. Atmospheric hydrators, the more prevalent type, are used in continuous mode to produce high-calcium and dolomitic hydrates. Pressure hydrators, on the other hand, produce only a completely hydrated dolomitic lime and operate only in batch mode. Generally, water sprays or wet scrubbers perform the hydrating process and prevent product loss. Following hydration, the product may be milled and then conveyed to air separators for further drying and removal of coarse fractions. An example of the manufacturing process of active lime is shown in Figure 11 and the steps are as follows: 1. Raw limestone goes through a crusher and a vibrator to reduce its size. 2. Qualified limestone (20 ~ 50 mm) is lifted by bucket elevator to the top silo of the preheater. 3. There are two level indicators (up and down) controlling the feeding amount, then they are separated averagely into preheaters’ individual rooms. 4. The limestone’s temperature rises to about 900℃ heated by kiln flue gas of 1150℃, about 30% of them are decomposed, and 5. They come into the rotary kiln by hydraulic rod, where the limestone decomposed into CaO and CO2. 6. The decomposed limestone is put into the cooler, where its temperatures drop to 100℃ and released. 7. The hot air (600°C) will come to kiln after heat exchange and mix with coal gas for mixture combustion. 8. The exhaust gas is released by the blower into bag deduster through multi-pipe cooler, then into the chimney though exhaust blower. 9. The limestone from the cooler will be transported to the limestone final product silo through vibrating feeder, chain conveyer, bucket elevator, belt conveyer. Gypsum The production process of gypsum powder is mainly divided into 5 stages: crushing, screening, grinding, calcination, storage and transportation as shown in Figure 13. 1. Crushing The mined gypsum ore raw material enters the crusher through vibrating feeder, and the crusher breaks the large-size gypsum ore into small particles smaller than 30mm, and then waits for further screening treatment. 2. Screening Page | 25 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Use a vibrating screen to separate incomplete large particles and impurities that mixed in crushed gypsum. Gypsum with suitable available size can be separated by controlling the diameter of sieve hole, which can be used as cement additive for sale. Or go straight to the next stage. 3. Grinding The screened gypsums are fed into the grinding mill uniformly and continuously by vibratory feeders for grinding. The ground gypsum powder is blown out by the air flow bulged by the mill blower and graded by the separator machine on the mill. The fineness qualified powder is collected by hydrocyclone and discharged through the powder outlet tube, is known as land plaster. Land plaster is sent by screw conveyor. As a soil conditioner or transported to calcination. 4. Calcination Calcination mainly uses the direct contact between high-temperature hot flue gas of boiling furnace and gypsum raw materials to complete the calcination and dehydration of gypsum powder. The structure and characteristics of dehydrated gypsum are also different under different heating conditions. Raw gypsum and anhydrite are often produced together, and anhydrite can be formed by calcining gypsum at 400 – 500 °C. Gypsum (CaSO4 ·2H2O) can be calcined and grinded to obtain β-type hemihydrate gypsum (2CaSO4 ·H2O), that is, building gypsum, also known as cooked gypsum or plaster. The model gypsum can be obtained when the calcination temperature is 190 °C, and its fineness and whiteness are higher than that of building gypsum. If raw gypsum is calcined at 400 °C or above 800 °C, floor gypsum can be obtained, its setting and hardening are slow, but the strength, wear resistance and water resistance of hardened gypsum are better than that of ordinary building gypsum. 5. Storage Transportation The calcined qualified gypsum powder is sent to the clinker warehouse for storage or into the workshop to produce gypsum board, cement and other gypsum products. Hardening of Plaster. The hardening of plaster is essentially a hydration reaction, as represented by the equation: 1 𝐶𝑎𝑆𝑂4 · 𝐻2 𝑂(𝑐) + 1.5𝐻2 𝑂(𝑙) → 𝐶𝑎𝑆𝑂4 · 2𝐻2 𝑂 2 This equation is the reverse of that for the dehydration of gypsum. The plaster sets and hardens because the liquid water reacts to form a solid crystalline hydrate. Hydration with liquid water will take place at temperatures below about 99°C., and that the gypsum must be heated above 99°C. for practical dehydration. Commercial plaster usually contains some glue in the water used or a material such as hair or tankage from the stockyards to retard the setting time in order to give the plasterer opportunity to apply the material. Page | 26 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Ceramic Industry Introduction Ceramics are commonly associated with "mixed" bonding, which includes covalent, ionic, and metallic components. There are no distinct molecules; rather, they are made up of interconnecting atoms. The vast majority of ceramics are composed of metals, metalloids, and nonmetals. Most commonly, they are oxides, nitrides, and carbides. Which inclined to the most widely accepted definition given by Kingery et al. (1976): “A ceramic is a nonmetallic, inorganic solid”. Brief History of Ceramics The history of ceramics is rich and spans thousands of years, reflecting the evolution of human civilization and technological advancements. Earliest Ceramics: The origins of ceramics can be traced back to the Stone Age, where early humans created a stone tool used for cutting and scavenging. This stone tool is made of Flint, Flint is a variety of chert, which is itself cryptocrystalline quartz. Cryptocrystalline quartz is simply quartz (a polymorph of SiO2) that consists of microscopic crystals. Flint is easily chipped, and the fracture of flint is conchoidal (shell-like), so that sharp edges are formed. They were made by a process called percussion flaking, which results in a piece (a flake) being removed from the parent cobble (a core) by the blow from another stone (a hammer-stone) or hard object. When a core assumes a distinctive teardrop shape, it is known as a hand axe (see Figure 15a), the hallmark of Homo erectus and early Homo sapiens technology, marking the beginning of ceramic technology. Ancient Civilizations: As civilizations developed, so did ceramic techniques. Ancient cultures produced intricate pottery and decorative items such as baked clay. The oldest samples of baked clay include more than 10,000 fragments of statuettes found in 1920 near Dolní Vestonice, Moravia, in the Czech Republic. They portray wolves, horses, foxes, birds, cats, bears, or women. One of these prehistoric female figures, shown in Figure 15b. Clay and Types of Pottery: The most common raw material utilized to make traditional ceramic goods is still clay minerals. Grain sizes of less than 2 μm are seen in the layered or sheet silicate clay minerals. They are aluminosilicates chemically. Mica is formed in nature by stacking layers together to create sheets, as seen in Figure 15c. Page | 27 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department The clay-water mixture holds its shape and becomes brittle and hard after drying. The clay body becomes robust and solid after fire at temperatures close to 950°C, and this has been utilized to make pottery. Throughout history, various types of pottery emerged, including earthenware, stoneware, and porcelain. Each type has unique properties and uses, reflecting the materials and techniques available to different cultures. Figure 15 a) Example of a stone tool made by percussion flaking, b) Baked clay Pavlovian figurine called the “Venus of Vestonice”, c) Large “grains” of mica clearly show the lamellar nature of the mineral. (a) (c) (b) Glazes: Glazes in ceramics began in ancient times, enhancing the aesthetic appeal and functionality of ceramic items. Egyptians introduced glazing around 3000 BCE to seal earthen ware pores. This involved coating fired objects with an aqueous suspension of ground quartz sand, sodium salts, or plant ash. The ware was then refired at a lower temperature, resulting in a glassy layer. Development of a Ceramics Industry: The industrial revolution brought significant changes to ceramic production, leading to mass production techniques and the establishment of ceramics as a major industry. This period saw the rise of companies specializing in ceramic goods, making them more accessible to the public. Page | 28 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Josiah Wedgwood led the revolution in ceramics, developing modern production and marketing methods, including the creation of improved unglazed black stoneware called "basalte" in 1767. The famous Wedgwood “jasperware” began production in 1775 and consisted of the following: one part flint, six parts barium sulfate, three parts potters’ clay, and one-quarter part gypsum. Historically, ceramic production was largely empirical, relying on consistent suppliers and avoiding changes due to complex systems. Today, with 100 years of research, processing and manufacturing are optimized based on basic scientific and engineering principles. Research in ceramics was spurred on by two main factors: Development of advanced characterization techniques such as X-ray diffraction and electron microscopy, which provided structural and chemical information; and Developments in ceramic processing technology. Types of Ceramics Ceramics are classed as traditional or advanced. Traditional ceramics include high- volume items such as bricks and tiles, whitewares and pottery. Advanced ceramics include newer materials such as laser host materials, piezoelectric ceramics, ceramics for dynamic random- access memories (DRAMs), etc., often produced in small quantities with higher prices. Figure 16 A comparison of different aspects of traditional and advanced ceramics Page | 29 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Traditional Ceramics Since silicate and aluminum silicate minerals are widely available, clay, refractories and glasses are inexpensive and form the backbone of the traditional high-volume products of the traditional ceramic industry. Their abundance also explains why this type of ceramic is found in nearly every part of the world. 1. Clay Products - Clay, an inexpensive ingredient, is found naturally in great abundance, often mined without any upgrading of quality. Clay products may be formed; when mixed in proper proportions with water and form a mass that is amenable to shaping. The formed piece is dried to remove moisture and fired at high temperatures to improve its mechanical strength. Clay- based products are classed into two: a. Structural clay such as bricks, tiles and sewer pipes in which structural integrity are important. b. Pottery such as earthenware, stoneware, porcelain and china which are primarily used for domestic, decorative and artistic purposes. 2. Refractories - are materials designed to withstand high temperatures without melting or decomposing and to remain unreactive and inert when exposed to severe environments (e.g. harsh chemicals and mechanical stresses). They are essential in various industrial process that involve intense heat such as in glass manufacturing and metallurgical heat treatments, cement kilns and power generators. 3. Abrasives – ceramics that are used to wear, tear, grind, or cut away other material. Common applications for abrasives include grinding, polishing, lapping, drilling sharpening and sanding materials. Naturally occurring abrasives include diamond, corundum, emery, garnet, calcite, pumice, rouge and sand. 4. Cements - are materials that, when mixed with water, form a paste that sets and hardens over time. 5. Glasses - are non-crystalline silicates that contain oxides such as CaO, Na₂O, K₂O, and Al₂O₃. The primary attributes of glasses are their optical transparency and the ease with which they can be fabricated. Figure 17 Traditional ceramics (from left to right): Clay products (pottery), refractories (bricks), abrasives (sandpaper), cement, and glass bottle This Photo by This Photo by Page | 30 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Advanced Ceramics The development of advanced ceramics is establishing a key role in technology, with unique electrical, magnetic, and optical properties driving new products. Advanced ceramics are typically synthesized with more controlled compositions and manufacturing processes than traditional ceramics. 1. Structural Ceramics - include silicon nitride (Si3N4), silicon carbide (SiC), zirconia (ZrO2), boron carbide (B4C) and alumina (Al2O3). They are used in applications such as cutting tools, wear components, heat exchangers, and engine parts. 2. Electronic Ceramics -include barium titanate, zinc oxide, lead zirconate, titanate, aluminum nitride and HTSCs. They are used in applications as diverse as capacitor dielectrics, travaristors, microelectromechanical systems, and packages for integrated circuits. 3. Nanoceramics - with structures and properties at the nanometer scale. These materials are widely used in cosmetic products such as sunscreens, catalysis, fuel cells and coatings. 4. Nitrogen Ceramics - ceramics that incorporate nitrogen into their structure. These materials are used in commercial production of thermocouple tubes, rocket nozzles, boats, and crucibles for handling molten metals. Many nitrogen ceramics are known for their hardness and wear resistance. 5. Magnetic Ceramics - magnets that were the first known to humans. Ferrite is a term used for ceramics that contain Fe2O3. These ceramics exhibit ferromagnetic behavior, making them useful in magnetic applications. 6. Bioceramics - Ceramics that are specially designed for use in medical and dental applications. These materials are engineered to interact with biological systems. Inert bioceramics include calcium phosphate, alumina and zirconia which are used in bone grafts, dental implants, hip replacements, dental crowns and bridges. Figure 18 Advanced ceramics (from left to right): structural ceramics (silicon nitride), electronic ceramics (capacitor), nanoceramics in sunscreens, nitrogen ceramics, bioceramics (dental implants) Page | 31 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Manufacturing Companies Local International Assitco Energy & Industrial Corporation CeramTech - Bagumbayan, Taguig City - Anaheim, California Legobuilders Inc Ironrock - Olongapo City, Zambales - Canton, Ohio EZ Rocks Co., Inc. HarbisonWalker International - Olympia, Makati City - Pittsburgh, Pennsylvania Mariwasa Siam Ceramics Inc. Grupo Lamosa - Sto. Tomas, Batangas - Nuevo Leon, Mexico PHOMI MCM Philippines SCG Ceramics - Makati City - Bangkok, Thailand Clay Product Composition Silica and alumina constitute the base elements of clay and are usually found in the following proportions: about 50% for SiO2 and 15–20% for Al2O3. Other components might be considered like barium (Ba), zirconium (Zr), strontium (Sr), rubidium (Rb) and manganese (Mn). However, these elements are always present in very small quantities and expressed in parts per million (ppm), while the proportion of the main components is expressed in percentage of the material volume. Moreover, chemical oxides commonly found in clay bricks are the following: Table 4 Chemical Constitution of Clay Compound Name Chemical Formula Silica SiO2 Alumina Al2O3 Iron or Ferrous oxide Fe2O3 or Fe3O4 Potassium oxide K2O Titanium dioxide TiO2 Sodium Na2O Calcium CaO Magnesium oxide MgO Page | 32 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Product Uses Bricks have been a fundamental building material for centuries, playing a crucial role in construction and architecture. Their durability, strength, and versatility make them an essential choice for various applications. These include Construction and Structural Uses, Environmental and Energy Efficiency, and Artistic and Decorative Uses. Construction and Structural Uses o Building Homes and Commercial Structures - Bricks are widely used in building construction due to their load-bearing capacity, thermal insulation, and fire resistance, providing a sturdy, reliable framework for homes, offices, and commercial structures. o Architectural Features - Bricks are utilized by architects to create unique and visually appealing features in buildings, offering a variety of colors, textures, and sizes to enhance design. o Paving and Landscaping - Bricks are versatile construction materials used in paving paths, driveways, patios, landscaping, and retaining walls, making them ideal for high- traffic areas and visually appealing outdoor spaces. Environmental and Energy Efficiency o Sustainable Building Material - Bricks, a sustainable building material derived from natural clay and shale, can be recycled and reused, thereby reducing waste and promoting environmental sustainability in construction. o Thermal Mass Properties - Bricks' thermal mass properties enable them to regulate indoor temperatures, enhancing energy efficiency and reducing the need for artificial heating and cooling in buildings. Decorative Uses o Sculptures and Art Installations - Bricks are utilized by artists and sculptors for creating intricate sculptures and installations, showcasing their artistic potential due to their versatility. o Interior Design - Exposed brick walls are gaining popularity in interior design, adding texture, warmth, and character to rustic country homes and modern urban lofts. Raw Materials The raw materials used in the manufacture of brick and structural clay products include surface clays, shales, and fire clays which are mined in open pits. Clay is crucial for brick manufacturing due to its plasticity, wet and air-dried strength, and ability to fuse together when subjected to appropriate temperatures, allowing it to be shaped and molded when mixed with water. 1. Surface Clays Surface clays may be the up thrusts of older deposits or of more recent sedimentary formations. As the name implies, they are found near the surface of the earth. Page | 33 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department 2. Shales Shales are clays that have been subjected to high pressures until they have nearly hardened into slate. 3. Fire Clays Fire clays are usually mined at deeper levels than other clays and have refractory qualities. Block Flow Diagram and Process Flow Diagram Figure 19 Block Flow Diagram of Clay Production Page | 34 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 20 Process Flow Diagram of Clay Production Detailed Manufacturing Process 1. Mining and Storage Surface clays, shales and some fire clays are mined in open pits with power equipment. Then the clay or shale mixtures are transported to plant storage areas. Continuous brick production, regardless of weather conditions, is ensured by storing enough raw materials required for many days of plant operation. Normally, several storage areas (one for each source) are used to facilitate blending of the clays. Blending produces more uniform raw materials, helps control color and allows raw material control for manufacturing a certain brick body. 2. Preparation Before combining the raw materials, the material is run through size-reduction machinery to break up big lumps of clay and stones. To manage particle size, the material is often treated through inclined vibrating screens. 3. Forming The initial stage of the forming process, known as tempering, results in a uniform, plastic mass of clay. Typically, to accomplish this, water is added to the clay in a pug mill (see Figure 18a), a mixing chamber containing one or more rotating shafts equipped with extended blades. The plastic clay mass is prepared for shaping after pugging. There are three principal processes for forming brick: stiff-mud, soft-mud and dry-press. a. Stiff-Mud Process - Water (10–15%) is introduced into the clay during the stiff-mud or extrusion process (see Figure 18b) to create plasticity. The tempered clay passes through a deairing chamber that keeps a vacuum of between 15 and 29 in. after it has Page | 35 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department been plugged of mercury (375–725 mm). By eliminating air holes and bubbles, de-airing increases the clay's workability and plasticity, which in turn increases its strength. b. Soft-Mud Process - Clays that contain too much water to be extruded using the stiff- mud method are best suited for the molded, or soft-mud, procedure. After mixing clays with 20 to 30% water, the mixture is molded into bricks using molds. Sand or water is used to lubricate the molds to prevent clay from adhering, resulting in brick labeled as "sand-struck" or "water-struck." In this way, brick can be made by hand or by machine. c. Dry-Press Process - Clays with very little plasticity are very well suited for this technique. After combining clay with a small quantity of water (up to 10%), hydraulic or compressed air rams are used to force the mixture into steel molds at pressures ranging from 500 to 1500 psi (3.4 to 10.3 MPa). Figure 18 a) Clay is thoroughly mixed with water in pug mill before extrusion, b) After mining, clay is extruded through a die and trimmed to specified dimension before firing (a) (b) 4. Drying Depending on the forming technique, wet brick from molding or cutting machines has between 7 and 30% moisture. Most of this water is evaporated in dryer chambers at temperatures between around 38 ºC and 204 ºC prior to the fire process starting. The length of the drying process, which varies depending on the type of clay, is typically 24 to 48 hours. To enhance thermal efficiency, heat is typically provided from the exhaust heat of kilns, though it may be created particularly for dryer chambers as well. To prevent brick cracking, heat and humidity levels must always be properly controlled. 5. Hacking Brick-loading a kiln car or kiln is known as hacking. The size of the kiln determines how many bricks are on the kiln vehicle. Usually, mechanical devices or robots are used to install the bricks. Page | 36 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Appearance is somewhat influenced by the setup pattern. When brick is arranged face-to-face as opposed to cross-set or face-to-back, the color of the brick will be more consistent. 6. Firing Bricks are fired between 10 and 40 hours, depending on the kiln type and other factors. The most common type is a tunnel kiln, followed by periodic kilns. Fuels can be natural gas, coal, sawdust, methane gas from landfills, or a combination of these. In a tunnel kiln (see Figure 19), bricks are loaded onto kiln cars, which pass through temperature zones. The heat conditions are carefully controlled, and the kiln is continuously operated. A periodic kiln is loaded, fired, allowed to cool, and unloaded, repeating the same steps. Firing can be divided into five stages: final drying, dehydration, oxidation, vitrification, and flashing or reduction firing. Figure 19 Brick Enter Tunnel Kiln for Firing 7. Cooling The cooling process starts after the temperature reaches its peak and is kept there for a predetermined amount of time. In periodic kilns, cooling times range from 5 to 24 hours, whereas in tunnel kilns, they seldom surpass 10 hours. The chilling process is a crucial step in the brick- making process since it directly affects color. 8. De-hacking After the bricks have cooled, de-hacking is the act of unloading a kiln or kiln car; robots are frequently used to carry out this task (see Figure 20). Bricks are graded, packed, and sorted. After that, they are either loaded onto trucks or rail carriages for delivery, or they are put in a storage yard. Page | 37 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Today, most brick comes packaged in self-contained, strapped cubes that may be divided into smaller, strapped packages for easier handling on the construction site. Forklift handling is made possible by the apertures in the cubes and packages. Figure 20 Robotic Arm Unloading Brick After Firing Ceramic Magnets (Ferrites) Ceramics can be magnetic too and they were the first magnets known to man. About 600,000 tons of ceramic magnets are produced each year making them, in terms of volume, commercially more important than metallic magnets. Ferrites is a term used for ceramics that contain Fe2O3 as a principal component. The largest market segment is hard ferrites that are used in applications including motors, windshield wipers, stripes on the back of ATM cards. In contrast, soft ferrites are used in cellphones, transformer cores, and magnetic recording. Ferrites can be further classified according to their structure: maghemite, garnets and hexagonal ferrites. Product Composition 1. Soft Ferrites or Cubic Ferrites (Maghemites, 𝜸-Fe2O3) Soft ferrites typically adopt a spinel structure, where the oxygen ions form a cubic close- packed FCC lattice, and the metal cations occupy interstitial sites in this lattice. Many different cation combinations may form a spinel structure. Listed in Table X are some of the common cubic ferrites and their chemical formula. Common Name Formula Nickel ferrite NiFe₂O₄ Zinc ferrite ZnFe₂O₄ Cobalt ferrite CoFe₂O₄ Lithium-titanate ferrite LiTiFeO₄ Manganese-zinc ferrite MnₓZn₁₋ₓFe₂O₄ Page | 38 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department 2. Ferrite Garnets Garnet is an example of a gemstone mineral. The chemical formula for garnets can be written as: 𝑋3 𝑌2 (𝑆𝑖𝑂4 )3 Where X and Y represent different metal ions. When Fe3+ ions occupy the Y-site, the garnet is classified as a ferrite garnet. In ferrite garnets, the X-site is typically composed of ferrite magnets are usually composed of rare-earth trivalent cations. Garnets also tend to be soft magnets but are not as widely used as cubic ferrites: they are more expensive. Listed below are some common ferrite garnets. Common Name Formula Andradite Ca3Fe2Si3O12 Yttrium iron garnet (YIG) Y₃Fe₅O₁₂ Gadolinium iron garnet Gd₃Fe₅O₁₂ 3. Hexagonal Ferrites Rather than a single structural type, hexagonal ferrites are a numerous family of related compounds with hexagonal and rhombohedral crystal structures. All of them are synthetic except magnetoplumbite. Common Name Formula Magnetoplumbite BaFe12O19 SrFe12O19 Ferroxplana BaxCo2FeXOX Product Uses Data Storage and Recording Magnetic recording is a major technology for electronic information mass storage. Its presence is seen in audio and video cassette tapes, floppy disks, computer hard disks, credit cards, etc. Magnetic tapes and floppy disks are collections of very fine magnetic particles supported on a flexible polymer such as PET. An advantage of these ferrite memories is that the stored information is maintained without the need for an external energy source, which is not the case for the semiconductor memories used in computers. Page | 39 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 21 Applications of ferrites in data storage and recording (from left to right): floppy disks, video casettes, magnetic strips in credit cards Loudspeakers One permanent magnet device is the loudspeaker, which is the largest single application of hexaferrites. The signal to be transformed to sound, typically from an amplifier, flows through the coil fixed to the end of the speaker cone; the interaction between the magnetic flux produced by the ferrite and the current results in an axial force on the speaker, which vibrates according to the electrical signal. Figure 22 Loudspeaker parts and hexaferrite magnets Tuners and Rod Antennas Ferrites are also used in antennas, to transform an electromagnetic signal into an electrical signal. Ferrites provide a compact device well adapted to small radio receivers. Page | 40 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 23 Ferrites in antennas Microwave Components The interaction between electromagnetic waves and the spin magnetic moments in ferrites has been used to create waveguides for microwaves. As microwaves travel along the waveguide, their behavior is modified. When microwave signals interact with the spins in the ferrite, the wave velocities are affected. Figure 24 A magnetron—a ferrite in microwave oven Other Uses: Household Appliances Starter Motors Refrigerator Doors and Magnets Transformers Page | 41 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Raw Materials Raw materials of ferrites are usually iron oxide (𝛼-Fe2O3) and the oxide or the carbonate of the other cations in the desired ferrite composition. These materials combine according to the overall reactions below (for cubic, garnets and hexagonal ferrites respectively). 𝐹𝑒2 𝑂3 + 𝑀𝐶𝑂3 → 𝑀𝐹𝑒2 𝑂4 + 𝐶𝑂2 5𝐹𝑒2 𝑂3 + 3𝑅2 𝑂3 → 2𝑅3 𝐹𝑒5 𝑂12 6𝐹𝑒2 𝑂3 + 𝐵𝑎𝐶𝑂3 → 𝐵𝑎𝐹𝑒12 𝑂19 + 𝐶𝑂2 M represents a divalent cation and R a rare-earth, trivalent cation. The 𝐹𝑒2 𝑂3 and the other carbonates are generally mixed and milled in ball mills. Figure 25 Strongly magnetic iron oxides from left to right: magnetite and maghemite To create ferrites, various metal ions or minerals are added to iron oxides. These added elements alter the electrical and magnetic properties of the ferrites which makes them suitable for different applications. Figure 26 shows some minerals that are added to iron oxides to make ferrites. Figure 26 From left to right: minerals that may be added to iron oxides for the production of magnetic ceramics (ferrites) –zinc oxide, nickel oxide, dysprosium oxide, samarium oxide, terbium oxide. Page | 42 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Block Flow Diagram and Process Flow Diagram The ceramic method, the oldest ferrite production technique involves the same classical techniques for fabrication of conventional ceramics. This explains the origin of the term magnetic ceramics. The four basic operations in the ceramic method are shown at the left-hand side of Figure X. However, due to the limitations of the ceramic method, many new methods have been developed. Most involve an improvement in one of the four basic operations in former. These novel methods appear on the right-hand side of Figure 27. Figure 27 Block Flow Diagram (BFD) of the four basic operations of the preparation of magnetic ceramics (ferrites) Figure 28 illustrates the process flow diagram for the manufacturing of ferrite magnets by SDM Magnetics, a specialized magnet company based in Hangzhou, China. The company utilizes techniques such as pelletizing, pre-sintering, dispersion, and machining in its production process. Page | 43 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 28 Process Flow Diagram of the manufacturing process of ferrites by SDM Magnetics Detailed Manufacturing Process This section outlines the four fundamental operations in ferrite manufacturing, as illustrated in Figure 27. Each operation includes two or more viable techniques: one for traditional ceramic methods and another for newer approaches. Powder Preparation a. Milling In chemical engineering, milling is a unit operation used to reduce the size of solid materials, such as ores of iron, to increase their processing effectiveness. This step, also known as comminution, involves crushing and grinding the ore to achieve a particle size that allows for even distribution of particle size and homogeneous composition. The most common type of mill used in chemical engineering is the ball mill. It consists of a cylindrical chamber lined with a protective material and filled with hard spheres or rods. As the mill rotates, centrifugal forces cause the grinding media to tumble and collide with the iron ores, leading to the reduction of particle size. Page | 44 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Milling can be carried out in a wet medium to increase the degree of mixing, by forming aqueous suspension of the raw materials. This process effectively breaks down the ore into finer particles. After milling, the suspension is dried out to obtain the powder. A narrow size distribution of spherical particles is important for compaction of the powder during green body formation. Grain growth during sintering can be better controlled if the initial size is small and uniform. Figure 29 From left to right: an industrial ball mill and a schematic diagram illustrating the g the movement of the media as the mill rotates about its axis b. Spray Drying Spray drying is a technique used to produce powders from liquid solutions, commonly employed in the preparation of ferrites. In this process, iron oxides and other minerals in solution are used to create finely sized powders. The concentrated solution is atomized at high pressure into fine droplets ranging from 100 to 500 micrometers in diameter. These droplets are rapidly dried by an upward stream of hot gas, causing the solvent to evaporate quickly. The resulting particles, which can be as small as 100 nanometers, are then compacted and calcined to form ferrites. A schematic representation of the spray-drying process is illustrated in Figure 30. Page | 45 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 30 Schematic spray-drying equipment Greenbody Formation a. Pressing Dry pressing is a straightforward compaction technique where dry powder is compressed between a die and punch system, typically using pressures of 5-10 MPa. In a double-action press, as shown in Figure 31, both the top and bottom punches are movable. When the bottom punch is in the lowered position, a cavity is created in the die, which is then filled with free-flowing powder. The powder mixture usually contains between 0 and 5 wt% binder. After filling the cavity, the excess powder is removed to ensure the surface is level with the top of the die. The powder is then compressed to the desired pressure, and the compacted material is ejected from the die. Figure 31 Stages of Pressing Page | 46 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department b. Slip Casting The slip, an aqueous colloidal suspension of ore powder, is poured into a mold with the desired shape. Water is absorbed into the porous mold through capillary action. Once the desired thickness has been achieved, the excess slip is poured out. The mold and the cast are then allowed to dry and undergo firing. Gypsum is commonly used for molds because it effectively absorbs water and allows for easy removal of the molded piece. This method has been used to produce Ni-Zn ferrites. The slip was prepared from precipitated Ni-Zn ferrite powders with a size of 30 nm. After molding, the pieces were dried at 50°C and then sintered at 1100°C. Figure 32 shows the simple illustration of the slip casting process. Figure 32 Schematic illustrating the drain-casting process: (a) Fill the mold with slip; the mold extracts liquid, forming a compact along the mold walls; (b) after excess slip is drained and after partially dryed, ceramic is removed. Page | 47 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Sintering Sintering is defined as the process of obtaining a dense, tough body by heating a compacted powder for a certain time at a temperature high enough to significantly promote diffusion, but clearly lower than the melting point of the main component. The ideal sintering process results in a fully dense material by elimination of the porosity. As particles fuse together and densify, smaller grains coalesce into larger grains which leads to grain growth. This growth reduces the total number of grain boundaries in the material. Figure 33 Coalescence of spheres resulting in a denser material Microwave Sintering Furnaces Electromagnetic fields can penetrate and propagate through various materials. When these fields interact with free and bound charges, as well as with magnetic moments, they transfer energy that can be used for high-temperature treatments. For example, barium hexaferrites have been successfully sintered using microwave techniques at 1230°C with a microwave frequency of 2450 MHz. This method has resulted in the production of high-quality ferrites. Page | 48 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Figure 34 A microwave sintering furnace and its schematic diagram Finishing The finishing of sintered anisotropic ferrites involves several key steps to achieve precise dimensions and surface quality. Initially, the surfaces of the sintered ferrites are ground to the specified dimensions. Due to their hardness and brittleness, these materials require the use of diamond tools for effective grinding. After grinding, the ferrites may undergo additional finishing processes such as lapping, polishing, and cleaning. Lapping, using a fine abrasive slurry, helps to achieve an even finer surface finish and tighter dimensional tolerances. Polishing further refines the surface, enhancing smoothness and reducing surface roughness. Finally, the ferrites are cleaned to remove any residual abrasive particles or contaminants. Page | 49 PAMANTASAN NG LUNGSOD NG MAYNILA (University of the City of Manila) COLLEGE OF ENGINEERING Chemical Engineering Department Glass Industry Introduction According to Morey (1938), glass can be defined as an inorganic substance that is continuous with and analogous to the liquid state. However, due to cooling from a fused condition, glass attains such a high degree of viscosity that it becomes rigid for all practical purposes. It is neither fully solid in the crystalline sense nor does it behave like a typical liquid. Instead, glass is often referred to as an "undercooled liquid" or an "amorphous solid" because it lacks a defined melting point and does not crystallize during cooling. Brief History of Glass Since ancient times, humans have used glass, as evidenced by archaeological findings. Primitive people across various regions shaped natural glass by hand. This type of glass, found in nature, originates from molten rock that cools so quickly it doesn't form the usual crystalline structure. Obsidian, the most common of these natural glasses, is typically translucent and black, though it can also appear red, brown, or green, with some varieties being transparent. It easily breaks into sharp, elongated fragments, making it ideal for crafting arrowheads, spearheads, and knives, a practice widespread among Stone Age cultures. In more advanced societies, obsidian was also highly prized for ceremonial uses and jewelry, with some artifacts displaying exceptional craftsmanship. Glassmaking or manufacturing dates back to ancient times, with evidence of Egyptians crafting glass as early as 6,000 or 5,000 B.C., primarily in the form of decorative sham jewels. These early glass objects were noted for their fine craftsmanship and remarkable beauty. During the medieval period, Venice held a

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