Acid Gas Incinerators
Acid Gas Incinerators are specially designed thermal oxidizers, which are used to reduce emissions from all volatile organic content (VOC) sources like furnaces or kilns. These incinerations burn the VOCs by thermal heating. The incinerators have high acid resistant refractory lining to withstand the high temperatures and the acidic nature of the gases. Gases which are treated in the acid gas incinerators include sulfuric acid, nitric acid and other acidic gases. The incinerators operate by raising the temperature of the material above its auto-ignition temperature, in the presence of oxygen, and keeping the material in this temperature for a sufficient amount of time, to complete the combustion to form carbon dioxide and water. While all incinerators do not have a waste heat recovery units, and these are known as straight acid gas incinerators, many of them come with a waste heat recovery unit to increase efficiency.
Acid Tanks
Acids such as sulfuric acid or hydrochloric acid are stored in large cylindrical tanks fabricated from carbon steel. At times these acid tanks are also used for mixing or processing acids. Even the tankers which transport acids are called acid tanks. Since the acid tanks are highly corrosive, they are often lined with a refractory lining, to prevent corrosion of the carbon steel. Usually while laying the refractory lining, the surface of the tank, made up of metal needs to be free from mill scale, rust, dirt and other impurities. The surface of the metal is then sandblasted and the layer of refractory lining is applied directly on the metal. This surface prevents the metal from coming in direct contact with the acid, thereby protecting the outer surface of the tank from corrosion related leakages and other problems. Owing to recent advances, the surface of the metal, after being sandblasted is now coated with a film of polytetrafluroethylene (PTFE), after which a layer of mortar is applied and over which the first layer of refractory lining is placed.
Air Heaters
Air heaters work on the principle of radiating heat into a passing fluid or air. In case of air heaters, the air is heated with the help of open-coil heaters, tubular heaters, strip heaters or quartz heaters. The air sucked is unfiltered, which may contain impurities, dirt, grease or water, which may reduce the life of the air heater. Hence, often air filters are used before the air enters the air heater. Another form of air heater is the compressed air heater, ideal for industrial applications. The compressed air heater uses the open wound heating coil and a high accuracy temperature sensor which allow the heater to adjust immediately to different air flow conditions, as well as fluctuations in the air flow pressure or velocity, without affecting the output temperature of the heated air. Air heating as the target source is best done in confined spaces so that the heated air is not lost to the atmosphere. Care needs to be taken that the air flow in the air heater is not stopped abruptly as it can cause damage to the heating coils.
Annealing Furnace
An annealing furnace is used to heat materials to a very high temperature, to alter the physical properties, the strength, and at times the chemical properties of the material. Annealing helps to relieve the internal stresses of materials, which can lead to failure while the material is in service. It also creates a homogenous internal structure, making the material more ductile and stronger. Annealing furnaces are commonly used in the metallurgical industry and glass manufacturing. The annealing furnace often operates between 300 C and 1200 C, depending on the material heated, which allows recrystallization of the metal, which makes them more stable. The furnace atmosphere can be controlled to allow oxygen contents between 2 to 8 percent as required and the cooling rate of the material can also be adjusted to take care of the flatness and thermal homogeneity of the material. Annealing furnaces need to provide good stability and uniform atmosphere to ensure good quality material is produced.
Arc Furnace
The arc furnace, often called the electric arc furnace, operates on as a batch melting process, in the metal industry, producing batches of molten metal known as heats. The electric arc furnace is mainly used to manufacture steel. The operating cycle of an electric arc furnace is called a tap-to-tap cycle which usually takes about 60 minutes per cycle, but using twin shell furnaces, the timing can be reduced to 35 to 40 minutes. The operating cycle is made up operations including furnace charging where the scrap is entered into the furnace, melting operation of the scrap, refining to remove the impurities, de-slagging to remove the oxidized impurities from the refining stage, and tapping to remove the purified liquid metal to the next batch operation. Then the furnace turn around phase occurs where the furnace is recharged again for the next heating operation. A modern electric arc furnace is known to process 150 tons of steel in every operation.
Ash Hoppers
Ash hoppers are a large, inverted pyramid shaped structures, used across several industries to collect the particulate matter such as ash, from expelled air. The hoppers are generally installed in groups to make them more effective and collect larger quantities. Most hoppers are made of steel. In a typical ash handing system, the ash is collected by an electrostatic precipitator or a baghouse, which are connected to the ash hoppers. These ash hoppers usually collect and send the ash down by gravitational force, and the ash is transferred to a storage silo. The ash hoppers often suffer from issues like no flow due to arching of the ash, flow rate limitation due to fine particle size distribution and flooding or uncontrolled flow, dust generation, agglomerated lumps of ash creating flow problems, and wear and tear of the structure. The ash hoppers used in some industries like the power sector are lined with refractory material.
Autoclave
Autoclaves are used in industries like composite manufacturing, wood treatment, and rubber processing and metallurgical industry. They are mainly pressure vessels which help to manufacture products which require exposure to high temperature and pressure. Autoclaves are generally pressurized with air or nitrogen, depending on the requirements of the material processed. They are heated either with gas or with electricity. There are two classes of autoclaves. One pressurized by steam, used in operations like rubber processing, and the other pressurized using heated gas, which offers more flexibility and control for the heating atmosphere. An autoclave furnace is usually made from carbon steel, and the most important part of the furnace is the door. The door is a fast opening door, which must adhere to high safety standards and should open and close quickly, easily and safely. A typical cycle of usage of autoclave involves closing of door, pressurizing the autoclave, starting the circulation fan, and heating the chamber, once the required temperature is achieved, lower the temperature at the specified rate and then depressurize the autoclave to stop the circulation.
Barring Furnaces
Barring furnaces are mainly used for the gold smelting process. One of the most common type of barring furnace in use is the tilting type furnace, which is flexible and can work under adverse conditions. The furnace size ranges from an A100 to A1000 crucible size, and this utilizes a chain drive to control the tilt of the electro-mechanical tilting process. The furnace is heating either by diesel or electricity and has a static cascade or carousel type of pouring table which provides the flexibility of pouring the molten gold into several different sized molds. The furnace is fired up for at least an hour before charging the crucible, post which the flux and the cake are mixed together into the furnace. Depending on the temperature in the furnace, the material inside fluidizes and can be poured into the molds. The barring furnace can also be used in other metal sectors like platinum, silver and aluminum smelting.
Beehive Kiln
A beehive kiln is a circular kiln with a domed roof. It was one of the earliest types of kiln invented by man. The kiln is now mainly used for making delicate jewelry out of metal clay, enamel and glass fusing. The fire to burn the kiln is at the bottom, which is fueled by either electricity or gas. The top of the kiln is shaped like a dome to create a better insulation effect. The ware is placed inside the kiln and the oxygen to aid the burning process enters through the fire box. There is a hole at the top of the kiln which allows the hot air which rises up to leave the kiln and maintain sufficient hot temperature in the kiln without burning the ware. There is a damper present at the top which regulates the size of the hole at the top to maintain the required temperature in the kiln.
Boilers
A boiler is an equipment which is used to generate steam, by heating up the water. Some boilers also heat up other materials. The boiler is usually made up of steel or alloy steel, and in some cases, wrought iron or copper and brass. Boilers are often lined with refractory material to contain the heat generated, and hence these refractory materials have strong insulating properties and are able to withstand high temperatures. Boilers are usually classified as fire-tube or water tube boilers and can be either high pressure, medium pressure or steam boilers. Boilers are used across many industries and usually are part of an entire heating system, which includes the boiler as the central heating device, piping with pumps and valves and controlling equipment to control the temperatures as desired. The boiler heats up the water or evaporates the water into steam, and then this steam or heated water is transported via pipe systems. The cooled water or the condensed steam is then brought back to the boiler and the whole process is repeated again.
Brick Laying Gunite
Gunite is the trademark name of spraying the mixture of cement, sand and water pneumatically on surfaces at high velocity, which starts the process of consolidation and settling simultaneously. Also known as Shotcrete, this method of using concrete was developed in the early 1900s, by a taxidermist, Carl Akeley, who used plaster in a similar fashion. In the later 1910s, this method of spraying concrete over a metal structure was introduced in the construction industry, mainly to patch deteriorated concrete. The method of spraying is ideal for creating thin and strong concrete linings and coatings and is used extensively in structures like bridges, canals, pools, docks, slopes and pipelines. In the steel industry, firebrick linings started getting replaced by Gunite concrete as they turned out to be less expensive, faster to install and lasted longer. Shotcrete can be either dry applied or wet applied. In the dry application method, the ingredients are placed in a hopper and sprayed through a hose through the nozzle, while the addition of water is at the nozzle controlled by the person spraying it. In wet application method, ready mix concrete with water is used and sprayed pneumatically on the surface.
Bricklaying
Bricklaying is the method of laying bricks one by one, in order to construct a structure. Bricks can be of different types including clay bricks, concrete bricks and other building materials in mortar. Brick laying involves, not only construction of new structures, but also repair of structures, and construction of partitions, arches and other structures. Bricklaying involves mixing mortar made up of cement, sand and water, along with a mortar additive, to get a smooth consistency. Then some mortar is scooped up and lay down an inch thick and spread across a few inches wide. A brick is then placed on the mortar, and is tapped into position. There is a spirit level used to check if the brick is aligned horizontally. Then, excess mortar is scrapped away and another brick is laid to form a layer of bricks. The next layer involves a similar process of spreading the mortar over the first layer of brick, placing the brick, checking its position and then scooping out the excess mortar.
Burners
Industrial burners are heating equipment which burn fuels like diesel, hot oil, or other similar fuels to generate heat needed for furnaces or reactors. Burners can be of various types, for different applications. Some of the types of burners include direct fired (baffle burners and air staged burners), radiant tube burners, regenerative burners, self-recuperative burners and high thermal release burners. The burners are designed to create a condition for the rapid mixing of the required amount of air and fuel, and produces a flame, which transfers the thermal energy to the furnace. In oil burners, the oil is atomized into a fine spray by a spray nozzle and air is supplied for combustion in the chamber. In the gaseous fuel burner, either the fuel is premixed with air before entering the burning chamber or a diffusion type methodology is used, where in a small amount of air and fuel are mixed and sent into the burner, while the rest of the air for combustion is supplied additionally into the chamber to aid in burning.
Calciners
A calciner is a cylindrical structure that rotates inside a heated furnace, and causing chemical changes in the material inside it, through indirect high temperature processing, in a controlled environment. The calciner removes the moisture from the ore, as well as removes the volatile impurities, such as sulfur and phosphorus. Often the terms, calciner and kiln perform a similar function, however, in general industrial terms, a calciner is referred to an equipment which uses indirect form of heat to process material. Calciners are used across a variety of industries, including metallurgy and cement production. The most popular type of calciners are the rotary calciners, where in radiation is the main form of heat transfer, with low gas velocities in the cylinder, due to indirect heating. As a result, fragile products and micro sized materials can be processed easily in the calciners. The other type of calciners in use are the fluid bed calciners, which are used to process materials like coffee, boric acid, magnesium sulfate and metallurgical ores.
Carbon Kilns
Carbon kilns, used for carbon regeneration, are indirectly fired kilns, which regenerate used carbon to its initial virgin state. These kilns have a rotating tube inside a hot combustion chamber. This tube takes in the foul carbon from a feed screw. The rotary motion of the tube imparts a slight momentum to the carbon which exposes the carbon to the regenerative atmosphere and heat transfer surfaces without over attrition. The residence time of the carbon in the tube can be adjusted by adjusting the tube’s rotational speed. As the carbon flows through the tube, which has angled filters and a slight incline, it is dried and regenerated. The general conditions for thermal regeneration are 650-750 C for a period of 10 to 30 minutes. The objective of regeneration of carbon is to remove the impurities accumulated during the adsorption process, recovering the original porous structure and reusing the carbon.
Casting
Casting is the engineering manufacturing process in which materials in a molten state are poured into a mold where they solidify to form specific shapes. The solidified part is then ejected out or broken out of the mold to complete the entire process. Casting enables to make a complex structure in one piece eliminating processes like machining, assembly and fabrication. Casting is used to mass produce different products, and can be used to make something as simple as a plastic toy to something as complex as a large gas turbine blade. Depending on the industry and the requirements, there are different types of casting processes, like sand casting, die casting, centrifugal casting, investment casting, high pressure casting, lost foam, plaster molding, resin shell molding and Shaw process. Raw castings often have irregularities in them due to imperfections in the molds and these are removed by process like cutting, grinding or shaving off the impurities, and this process is known as fettling.
Ceramic Fibre Lining
Ceramic fiber is a manmade mineral fiber which mainly consists of alumina and silica. These fibers emit very low heat from the furnace and have high energy saving properties, owing to their low thermal conductivity. Additionally because of their low density and low thermal inertia, these fibers facilitate the controlling of temperature, in the furnace. As a result, these ceramic fibers are used extensively as the inner linings in furnaces in industries like steel production, where high temperatures are required to produce the material. Ceramic fiber linings are used in industries which require equipment to have low thermal conductivity, low heat storage, good thermal shock resistance, light weight as well as corrosion resistance. Ceramic fiber lining is mainly used in equipment like furnace, kiln, reformer, boiler, furnace door linings, expansion joint seals, cast mold wrapping, pressure and cryogenic vessel fire protection, high temperature filtration, equipment nuclear industry equipment and incineration equipment.
Ceramic Fibre
Ceramic fibre is a manmade mineral fibre made from high purity aluminosilicate material by controlled high temperature furnace melting and fiberizing process. The fibre is white and odorless, suitable for high temperature applications. The advantage of ceramic fibres include their light weight, low thermal conductivity, high temperature stability, strong handling strength, low heat storage, thermal shock resistance, fire and flame proof, chemical resistance and compatibility with most acids and alkalis (a few exceptions include hydrofluoric acid, phosphoric acids and concentrated alkalis). Ceramic fibre varieties include aluminum silicate fibre, polycrystalline alumina fibres and aluminosilicate fibres which include Cr2O3, ZrO2, or B2O3. They are mainly available in the form of ceramic fibre cotton, felt, blanket, modules, paper, cloth, tape, and ropes. Ceramic fibre blankets are used for heat insulation in the petrochemicals, metallurgical and power generation industries, while ceramic fibre cloth find use in fire doors, insulated industrial furnace insulation, heat pipes and containers. The ceramic fibre ropes are used in industrial furnace expansion joints and pipe insulation windings.
Combustors
A combustor (also known as burner) is the component of a gas turbine in which the fuel is mixed with air and burnt to produce a high temperature exhaust gas which is used to turn the gas turbine and generate power. The combustor is also used in modern passenger and military aircraft engines to produce the thrust. Combustors are often lined with refractory materials, which allow the turbines to handle high temperatures, have better insulation value, higher resistance to thermal shocks, lowered weight and higher combustion efficiency. Combustors can be single or dual fuel and there are three main types of combustors. The can combustor are self-contained cylindrical combustion chambers, while the cannular combustors have discrete combustion chambers like the can combustor but share a common ring casing so that the chambers can communicate with each other via holes or connecting tubes. The annular combustors are fully annular, and have a continuous liner and casing in the ring.
Cracker
Crackers are used in the petrochemical industry to crack (break down0 feedstocks like naphtha, natural gas, refinery off gas and other long chain hydrocarbons into smaller molecules usually olefins like ethylene and propylene. The temperatures inside the crackers often reaches over 1000 C. The design of the cracker depends on its feedstock and the ethylene produced from the cracker is used to make various petrochemical products like polyethylene, polyvinyl chloride and ethylene oxide derivatives. The raw material is fed into the furnaces under severe conditions, to produce gases like ethylene, propylene and other byproducts. This outlet stream is water quenched to remove the undesirable byproducts and prevent further reactions. The gas is then compressed and dried and then separated to get the pure ethylene used to create further downstream products. Crackers are lined with refractory linings to lower the heat losses and to provide better insulation properties. Types of crackers include steam cracker, hydro crackers, fluid catalytic crackers, and deep catalytic crackers.
Cremators
A cremator is an equipment used to carry out the cremation process for a human or animal body. The body’s cremation inside the cremator is carried out at 1400 to 1800 F, which helps reduce the body to its basic elements and only ashes are left. The cremator is preheated to a set point and a body is transferred inside the cremator through a mechanized door to prevent heat loss. The flames produced inside the cremator are fueled by natural gas or any other liquid fuel. The heat in the cremator dries up the body and only the bones remain. The cremator is lined with a heavy duty high density refractory brick lining to retain the intense heat. While these bricks do get worn out due to repeated use, they can be replaced easily once they reach half their thickness.
Dryers
Industrial dryers are used to lower the moisture content of bulk materials. Most commonly used industrial dryers include fluidized bed dryers, rotary dryers, rolling bed dryers, conduction and convection dryers, pharmaceutical dryers, suspension dryers and dispersion dryers. The most basic type of dryers are the hot air dryers, wherein the ambient air is heated at a high temperature to lower moisture content. The desiccant dryers dry materials by passing the hot air through a molecular sieve desiccant which removes moisture from the air. The compressed air dryer uses compressed air in an open loop to remove moisture from the material. A special type of dryer uses infrared energy to heat materials and is used in the plastic industry. Most dryers are made up of stainless steel with a lining of refractory material in the inside to provide better insulation properties.
Ducons
Scrubbers are used in industrial applications to reduce pollution from exhaust streams, by removing the particulate matter. There are two types of scrubber systems – wet scrubber and dry scrubber. The scrubbers are known by their brand name ‘Ducon’, as manufactured by the company named Ducon. Wet scrubbing involves the contact of the target particulate matter with the scrubbing solution which can be water or any other reagent. The dry scrubbing is mainly used to remove gases like sulfur dioxide or hydrochloric acid from combustion processes. The dry scrubber involves introducing the acid gas absorbent material into the gas stream and then removal of the particulate matter in the flue gas as well as the reacted material from the gas stream. Dry scrubbers usually generate a dry waste product which can be easily disposed in a conventional fly ash handling system. In the dry scrubber systems, lime, trona, activated carbon or other dry reagents are used to remove the polluting gases.
Multi Hearth Furnaces
A multi hearth furnace, also known as multiple hearth furnace, is made up of several circular hearths or kilns, which are superimposed on each other and is used for continuous production and calcining of materials. A multi hearth furnace is usually employed when a large volume of material needs to be thermally processed. The limitations to the multi hearth furnace is that the material which needs to be processed should be moderately uniform in size and there should be a steady continuous feed. The hearths are generally like floors inside a large cylinder and alternate between in-hearth and out-hearth with the in-hearths having a large hole at the center for the material to pass into the hearth below it and the out hearths have holes towards the periphery of the hearth for material to pass through the hearth below. Multi hearth furnaces are made up of a steel shell, with a refractory lining to withstand high temperatures and provide good insulation.
Electric Furnace
An electric furnace is a furnace that runs on electricity and is used to achieve high temperatures to melt and alloy metals and refractories. The electricity does not have any electrochemical effect and just heats up the material inside it. Electric furnaces are generally arc furnaces or induction furnaces, though a third type called resistance furnace is used specifically for the production of silicon carbide and electrolytic aluminum. In the resistance furnace, the material being processed serves as a resistance element. Most electric furnaces are used in the manufacture of steel. The electric arc furnace, the arcs are struck into the metal bath from vertically positioned, graphite electrodes, while in the induction furnace, a coil carrying alternating electric current surrounds the chamber of metal. The circulation of these currents produce very high temperatures, melting the metals inside the chamber. The lifespan of an electric furnace is 20 to 30 years, and these furnaces require less maintenance compared to other kind of industrial furnaces.
Flare Linings
Flare systems are lined with refractory linings for temperature maintenance and control of flue gas retention time which is vital to ensure efficient destruction of pollutants. These refractory linings are called flare linings. The typical flare linings include spray linings, lightweight castable refractories, ceramic fiber blanket and other materials which protect against chemical attacks to the refractory linings. Flare tips are also lined with refractory material to prevent metal erosion. Flare linings are often reinforced with streel needles to provide tensile strength and ensure that the material does not produce any expansion or contraction shear planes.
Flares
Flares are safety devices used in the petrochemical and refining industries to burn out the excess hydrocarbon gases which cannot be recovered or recycled. The excess hydrocarbons are burnt in an environmental friendly manner in the flare, instead of releasing the vapors directly into the atmosphere. A flare system usually consists of a flare stack and pipes that feed the gas into the flare. There are different types of flare systems like the elevated flares where the flare tip is 20 to 150 meters about the ground, and ground flares where in the tip is about 2 to 3 meters above the ground. The ground flare is often surrounded by a heat resistance fence to act as a safety zone. Flares can be used for different kind of services like acid gas flare, cold dry flare and warm wet flare. Reasons for flaring hydrocarbons can include safety and emergency reasons, maintenance, managing gas during compression and processing and at well sites to recover oil.
Furnaces
Furnaces are equipment used across industries to provide high temperature heating to process different materials. The heat energy to the furnaces may be provided by fuels like diesel, fuel oil, natural gas, or electricity and induction. The basic components of the furnaces include radiant section, convection section, radiant coil, burner, soot burner, stack, insulation, foundations and access doors. All furnaces are lined with refractory material to provide insulation and protect the outer cover from intense heat. The key types of industrial furnaces include blast furnaces, open hearth furnaces, induction furnaces, multi hearth furnaces, electric arc furnaces, bell furnaces, aluminum melting furnaces, box furnaces, tube furnaces, rotary furnaces, and reverberatory furnaces. An efficient furnace is usually designed to consume less fuel and heat the material as much as possible, in the given time. Depending on the material to be processed, the furnace temperature, fuel and the type of furnace are determined.
Glass Tank Maintenance (Glass Fused Steel Tanks)
A glass lined steel tank or glass fused steel tank are storage tanks in which steel and glass are fused together to form a material which has the strength and flexibility of steel and the corrosion resistance of glass. These special tanks are used to store drinking water, for anaerobic digestion processes, leachate storage, fire water storage, desalination and dry bulk storage. The steel panels are baked at 840C to create a highly durable surface bond via the ultra-glass coating process in which the inert glass layers are fused with steel. The tanks are available in domed steel, glass lined and geodesic roof system varieties. The glass fused steel tanks have the advantage of long life span, flexibility to remodel and provide optimum corrosion resistance. A properly maintained glass fused steel tank can have a life span of 40 to 60 years, while the upfront installation costs are higher, in the long term, they prove to be more economical.
Glass Tank/Furnace
Glass Tank or glass furnace is the equipment in which molten glass is manufactured. There are different furnace designs and are dependent on the quality of glass to be produced and the type of glass production. The key types of glass furnace include pot furnace (batch process), day tanks, recuperative, cross fired regenerative, end port fired regenerative, oxygen fired unit melters and electric furnaces. The continuous furnaces are used to mass produce glass and the heat is mainly produced by either natural gas or oil. The furnace’s melting capacity is expressed as number of tons of glass produced per day, since it is a 24 hour operation. Depending on the furnace and the type of glass produced, the capacity of the furnace can vary from 20 tons per day to greater than 700 tons per day. The temperatures in the furnace often reach 1500 C and this is contained with the help of refractory linings in the inside surface of the furnace.
Gunning
Gunning is the technique used to spray the material through a nozzle at high speed. Standard gunning materials are made of magnesia, alumina or silica base. Gunning is mainly used for the hot repair of ladles, melting furnaces and relining of refractory material. The two basic methods of gunning are dry gunning and wet gunning. With dry gunning, the material is discharged from the machine with 5% moisture and fed into the nozzle via an air stream where the required amount of water is added to be sprayed on the surface required. In wet gunning, the gunning material is mixed with water in a mixer and the material is dispersed with the help of compressed air, and an additional liquid bonding or hardening material is added if required. Wet gunning suffers from the disadvantage of clogging if wet material is already present and the machine is not in use. The different types of gunning machines include rotary and pressure vessel gunning machines.
Heat Generation Furnaces
A furnace is an equipment in which heat is generated and transferred to another material in order to bring about physical and chemical changes to the material. The heat generation furnaces generate the heat via combustion of solid, liquid or gaseous fuel. These furnaces produce a hot gas which transfers heat to the material via radiation and combustion. Solids are usually heated directly, while liquid materials are heated indirectly. Furnaces have inner lining with refractory material and the material is introduced into the furnace by chutes, conveyors or pipes. The furnace can run on batch mode or continuously. The heat generation furnaces can be direct fired, over, under or side fired.
Heat Treatment Furnaces
Heat treatment involves the use of thermal energy to alter the physical and at times the chemical nature of a material. Heat treatment furnaces are used to carry out the process of heat treatment, especially in the metallurgical industry. Furnaces used for heat treatment can be categorized into batch furnaces and continuous furnaces. The batch furnaces are usually manually loaded and unloaded, with the continuous furnaces have an automatic conveying system which continuously takes the material into the chamber furnace for treatment. The different types of furnaces include box furnace, car type furnace, elevator type furnace, bell type furnaces, pit furnaces, salt bath furnaces and fluidized bed furnaces. All the furnaces have components including a refractory chamber made with insulating refractory materials to retain the heat, a hearth/kiln, burners, chimneys and charging and discharging doors. The heat treatment furnaces use oil, natural gas, coal or electricity as fuel.
Hot Gas Generators
Hot gas generators are used to dry raw materials like ore, limestone, phosphates, gypsum, or coal to reduce their moisture content before they are further refined or processed. The hot gas generator consists of a combustion chamber to burn the fuels and allows the mixing of the process air or recirculated air with the combustion gases to obtain the required temperature in the hot gas flow. Hot gas generators can work on a number of fuels including coal, oil, natural gas, biogas, lean gas, LPG, syngas, biomass, and lignite. While all hot gas generators do not have refractory linings, some of them do, to provide heat insulation. Hot gas generators are usually used in conjunction with grinding plants, drum type dryers, fluidized bed furnaces, flash dryers and spheroidizers. The combustion chamber is made up of steel and in some cases, lined with refractory lining and can withstand up to 1200 C temperatures.
Incinerator Stack Lining
Stacks inside incinerators are lined with refractory materials to provide heat insulation and protect the out shell from thermal shocks and prevent corrosion. These linings of refractory materials are known as stack linings. The stack liners can be one to three inches thick and act as a safety feature, preventing the possibility of fire. For temperatures above 450 C, the stack should be lined with refractory material. The selection of the refractory material for the lining depends on the components to be processed in the incinerator. The refractory lining is usually pneumatically or gun applied and is 2 inches thick over a reinforcing material like steel mesh. The mesh is held in the stack via studs and nuts.
Kiln Cars
The kiln cars are used in the refractory and ceramic industry to shuttle fired and unfired ware in and out of the furnaces. The earlier kiln cars were constructed using heavy refractory materials, but these proved to be energy inefficient. Over the years, the weight of the kiln cars has reduced considerably. The kiln cars are particularly used in the tunnel kiln where the unfired wares are pushed from outside and transported through the kiln on the car, while the temperature is increased steadily, by the hot gases. When the ware reaches the combustion chamber, they are fired directly or indirectly by fuel or electric power. Then the kiln car carries the fired ware outside to the cooler atmosphere. Most of the kiln cars are custom designed to the type of kiln they are used for.
Ladles
A ladle in the metallurgical industry is a vessel that is used to transport and pour out the molten metals. Ladles are also used in the ceramic industry. Ladles can be categorized as casting ladle – to pour the metals into molds to produce the castings, transfer ladle – to transfer molten metal from one process to another, and treatment ladle – to undertake changes inside the ladle, an example is converting cast iron to ductile iron by addition of various elements inside the ladle. All ladles are fitted with a refractory lining, which help to prevent corrosion, protect the outer vessel from high temperature and provide thermal stability to the ladle. Earlier ladles were lined with pre-cast firebricks, but now a days, refractory concrete is used extensively. Ladles can have lip pour design, teapot spout design, lip axis design and bottom pour design, depending on their use. Ladles can be open-topped or covered and covered ladles usually have a dome shaped lid to contain radiant heat.
Launders
Launders are used for liquid metal transfers from the furnaces to their casting machines. The launders are lined with refractory materials to provide an inert atmosphere and protect the outer shell of the launder. The launders come in various shapes like Y shaped, V shaped, elbowed and others. The launders enable the connection of the furnaces to the casting machines, and can be fully integrated with the degasser unit and filter box. The refractory linings are pre-molded and can be removed and replaced once their lifetime is over. All launder systems are optimized for minimal heat losses, low casting temperature and homogenous flow of the metal.
Lime Kilns
A kiln which converts limestone into quicklime by the calcination process is called a lime kiln. The calcination takes place at 900 C, and the slacked lime is formed by mixing water with quicklime. The types of lime kilns include shaft kilns, counter current shaft kilns, regenerative kilns, annular kilns, and rotary kilns. Rotary kilns are one of the more popular type of lime kilns, and are usually made of a rolled steel outer shell and a refractory lining inside to insulate the steel shell from high temperature inside the kiln. The refractory lining also protects the kiln from corrosion and may be made up of refractory bricks or cast refractory concrete. The limestone is heated in the preheater at 800 C and then from 1200 to 2000 C to make lime. The burn temperature and the time in the kiln depends on the type of rock which is processed.
Oil/Gas/Bagasse Fired Boilers
Boilers are equipment which generate steam or hot water by heating water with a fuel source like oil, gas or bagasse. Oil fired boilers are used in regions where gas is not available. The oil can be diesel, fuel oil or even a blend of diesel with biodiesel or any other biofuel. Gas fired burners use natural gas, LPG, propane or butane as fuel to heat water. Bagasse fired boilers use bagasse as fuel to heat the water. Bagasse fired boilers have good efficiency levels and are bagasse being the waste product of the sugarcane industry, can be used to meet the high energy requirements of sugar production.
Ovens
Industrial ovens are heated chambers which are used for a variety of purposes including drying, curing or baking components. The ovens can be continuous or batch processes and depending on the industry they are used in, can have a variety of temperature ranges, sizes and configurations. The common types of ovens include curing ovens, drying ovens, baking ovens, reflow ovens, batch ovens, conveyor ovens and clean room ovens. The ovens are lined with refractory linings to provide insulation and protect the outer shell. The ovens are used across applications like aerospace, composites, carbon-fiber manufacture, auto component manufacture, healthcare products, chemical processing, food production, and electronics. Ovens also find use in the powder and paint industry, preheating of molds and other tooling in the plastics and fiber industry.
Quench Towers
A quench tower is used for cooling heated exhaust gases from various equipment like incinerators and furnaces. The exhaust gas from the high temperature sources is cooled down with water vapor to the saturation temperature of the gas. The quench tower is used as pre-cooler for scrubbers and precipitators. The quench tower is made of corrosion resistant materials like steel and uniform water spraying takes place by special spray nozzles. Quench towers can be both horizontal flow and vertical flow. Quench towers are often lined with refractory material at the dry and wet zone interface. Fouling arises in the tower since it acts as a heat exchanger with the incoming gas, and many impurities may come along with the gas. Often the scrubbers or the compressors connected with the quench towers have fouling issues, due to the impurities gathered in the quench tower.
Ramming Moldable Refractory Casting
Ramming moldable refractories are ready mix powdered refractory materials usually tempered with water, that cannot be extruded by have suitable properties to permit ramming of the material into a particular cast, to form a monolithic structure. Ramming masses can be dry or wet. The ramming refractories can be rammed by a pneumatic hammer or a mallet into a cast. The ramming refractories usually have low to high alumina, can be air or heat or set, and are phosphate bound. The products are usually available in a semi dry condition with moisture content up to 3%, and can be hand rammed as well. Due to the low moisture content, a very dense material can be achieved with very little shrinkage.
Reactors
Reactors are vessels in which reactions between materials take place. Chemical reactors are designed for chemical reactions, while nuclear reactors are utilized for nuclear reactions. Chemical reactors can be of different types, including batch reactors, continuous stirred tank reactor, plug flow reactor, semi batch reactors and catalytic reactors. The commercial type of nuclear reactors include pressurized water reactors, boiler water reactor, pressurized heavy water reactor, gas cooled reactors, light water graphite reactors, and fast neutron reactors. In a reactor, the materials are charged inside and the chemical process takes place at a particular temperature and pressure, depending on the material. While batch reactors are used for biological reactions like brewing, pulping or production of enzymes, the continuous reactors are used for chemical and petrochemical production. Reactors often are lined with refractory materials to increase insulation, prevent corrosion and protect the outer shell from the chemicals mixed in the reactor.
Reformers
Reforming is the technique in which the molecular structure of a hydrocarbon is rearranged to change the properties of the hydrocarbon. Reforming is can be done either thermally or by using a catalyst. The reactors which undertake the reforming process are called reformers. The reformers react the raw materials at high temperatures. The steam reformers are used to make hydrogen, while the catalytic reformers are used in the chemical industry which convert the naphtha to reformates which are high premium blending stocks for gasoline. The catalytic reformers have catalysts in them to convert the products, and these catalysts are regenerated in-situ to make the process cyclic. Often the reformers are operated in multiples so that when one reformer is undergoing regeneration of catalysts, the other reformers can be used for the conversion process. Due to the high temperature conditions of the reformers, they are lined with refractory material to provide insulation and protect the outer cover from corrosion.
Roasters
In the metallurgical industry, roasters are used to undertake the process of roasting, wherein the ores are purified by undergoing a series of gas solid reactions at high temperatures which include oxidation, reduction, chlorination, sulfation and pyrohydrolysis. In a roaster, the ore is heated in a regular supply of hot air in a furnace at a temperature below the melting point of the metal. Before the roasting, the ore is semi-purified by froth floatation process. This concentrate ore is mixed with other materials to facilitate the process. Roasting is generally used to convert the sulfide to an oxide, and sulfur is released as sulfur dioxide gas. The roasters are of different types, including fluidized bed, multiple hearth, flash, rotary or blast roasters. The advantages of using roasters include high energy efficiency, useful recovery of sulfur, oxide ores can be roasted because of the exothermic nature of the oxidation reactions. The disadvantage of the roaster is that it can be highly polluting.
Rotary Kiln
A rotary kiln is an equipment in which materials are heated at high temperature to bring about physical and chemical changes to the material. Rotary kilns are used for the production of cement, lime, refractories, alumina and iron ore pellets. The rotary kiln is a cylindrical vessel, inclined marginally in the horizontal direction which rotates around its own axis. As the kiln rotates in a very low speed, the material which is fed from the upper end of the kiln moves downwards as well as undergoes circular motion, and can be subjected to hot gases in the same direction or opposite direction of the flow of material. The hot gases can be generated either from an external furnace or a flame inside the kiln. The basic components of the kiln include the shell, the refractory lining, support tires and rollers, and internal heat exchangers. The fuel used for heating the air can be gas, oil, or coal.
Shotcreting
Shotcreting is the technique employed in construction, in which concrete or mortar is conveyed through a hose and pneumatically sprayed at high velocity onto a surface, like steel rods, mesh or fibers. These surface also provide stabilization when shotcreting is used to construct slopes and tunnels. Shotcrete includes both dry mix and wet mix versions. Shotcrete is different from Gunite which is the trademark name of the dry mix version, registered by Allentown Equipment, the oldest manufacturer of gunite equipment. The dry mix version of shotcreting involves placing the dry ingredients into a hopper and conveying them pneumatically through a hose with the person operating the equipment, adding the required quantity of water, at the nozzle. The advantage of this process is that the amount of water added can be controlled. In wet mix shorcreting, the ready mix concrete with added water, is pumped to the nozzle and compressed air is introduced at the nozzle to push the mixture out.
Soot Blowers
Soot blowers are installed in most boilers to remove the entrained soot and ash which are susceptible to slagging and fouling. The soot blower directs a stream or number of streams of cleaning medium (either water or steam), at the ash deposits so that they get dislodged owing to the impact of the jets. The soot blowers consist of four key parts – nozzles for blowing the fluid, elements for conveying the fluid, drive system for rotating or advancing the element and the control system. Soot blowers are of four main types – wall/short retractable, rotary, retractable and rake type. Not all boilers require soot blowers. Boilers working on clean fuels like natural gas do not have any soot produced and hence do not require soot blowers. Steam is the most common blowing medium in a soot blower, though compressed air has the same effectiveness. Sometimes a special variety of soot blower called acoustic soot blowers are used which use sound waves generated at low frequency to produce rapid fluctuations, causing vibrations in the ash deposits, and loosen them to fall into the gas stream.
Stack Lining
Stacks are necessary equipment which are needed to be added to provide the buoyancy to the exhaust gases as they release into the atmosphere. The stacks are often lined with refractory material, to prevent corrosion and protect the outer shell of the stack from heat. The refractory material lining the internal section of the stack should be compatible with the chemistry of the gases leaving the stack. The refractory used is usually three part acid resistant aggregate and one part lumnite cement. The lining is usually applied using pneumatic or gun sprayed method and is usually 2 inches thick over the reinforcing material like steel mesh.
Stress Relief Furnaces
The purpose of the stress relief furnaces is to raise the temperature of the component in it to slightly below the transformation temperature, and holding the component in that temperature for a while, which eliminates the internal stresses caused due to operations like welding, machining or cold forming. Upon reaching the required temperature in the stress relief furnace, the material is then cooled at a controlled rate. The precise temperature, hold times and cooling rates are dependent on the material and other factors. This method is extensively used in power generation, oil & gas, mining and petrochemical industry on piping systems and small to large structural components. The stress relief furnaces can be gas fired or oil fired. Due to the high temperature achieved within the furnace, they are internally coated with refractory material to protect the outer shell and provide insulation.
Sulphur Furnace
A sulfur furnace is a large horizontal cylindrical vessel made up of carbon steel and lined internally with a refractory brick to provide complete combustion of molten sulfur with oxygen to produce sulfur dioxide. The reaction is extremely exothermic which results in the furnace reaching high temperatures. An air stream enters from one end of the furnace while liquid sulfur is fed through the same end via a sulfur gun, which has a simple spray nozzle or a spinning cup. Sulfur furnace are usually coupled with boilers to remove the heat from the exothermic reaction. A typical sulfur furnace has two to three baffles to provide sufficient turbulence and mixing to ensure complete combustion of sulfur to sulfur dioxide. These baffles can be checkered walls or segmental baffle walls.
Tap Holes
The tap hole is an essential part of a blast furnace and is used for tapping the hot metal from the furnace, with its location just about the floor of the hearth. The operation of the blast furnace is a continuous one as a result of which the liquid iron and slag are produced throughout its operation period. This iron and slag accumulate in the hearth but need to be removed at regular interval to ensure smooth operations of the furnace. Hence a tap hole proves to be useful to help in this removal. Large furnaces usually have 2 to 4 tap holes and the drainage of the slag and hot metal is continuous by periodically drilling and plugging the holes where one tap hole is open while the others are shut. Medium or smaller furnaces have one tap hole which is operated periodically. The tapping process determines the in-furnace gas pressure and residual amounts of metal and slag in the hearth.
Thermbond Installation
Thermbond is the brand name of the refractory mixes supplied by Thermbond. The installation of Thermbond involves mixing the refractory mix with a paddle type mixer, ensuring the right amount of refractory material and liquid activator. It is important to mix only that much material as required. First the required quantity of liquid activator needs to be added, post which the correct ratio of the dry formulation needs to be mixed into the liquid activator. This mixture needs to be mixed exactly for the stipulated amount of time, post which the setting process starts and this can make the mixture too thick for application. Water should never be used as the liquid component as it is not compatible with the dry mixture and can cause failure including explosive spalling. The refractory mix should be immediately poured in the area where it needs to be cast, and curing of the mix ends when the exothermic reaction stops and the material cools down to the ambient temperature.
Tunnel Kilns
Tunnel kilns are continuously operated car bottom kilns, which are tunnel like. The pushers move the train of kiln cars non-stop within the kin in a predetermined rate. Tunnel kilns are mainly used in the ceramic industry which require high volume production in a continuous manner. In the tunnel kiln, only the central portion is directly heated. From the cool entrance, the ware is transported slowly into the kiln on a kiln car. The temperature increases steadily as the ware reaches the middle of the tunnel where it is subjected to direct heating. The ware then moves on to the other end of the tunnel kiln, where the temperature drops steadily and the finished ware exits the kiln at near room temperature. A continuous kiln is energy efficient, since the heat given off by the cooling section is recycled to heat up the entrance section. The walls of the tunnel kiln are lined with refractory bricks to provide insulation and protect the outer shell of the kiln.
Vertical Shaft Kilns
Vertical shaft kilns were one of the earliest forms of kilns used to produce cement. The kilns comprise of one or more rectangular vertical shafts, which are well insulated and lined with refractory material. The material is loaded on top of the shaft, with the fuel part way up the shaft. The fresh feed from the top of the shaft is dried and then heated to 800C where decarbonisation takes place, and it proceeds down progressively as temperature rises. Below the burner, the hot material transfers the heat and is cooled by the combustion air. This is a continuous process, and the degree of burning can be adjusted by changing the withdrawal rate of the material. The advantage of the vertical shaft kiln is that they have low capital cost and require less maintenance and are comparatively more fuel efficient. However, they suffer from the disadvantage of low production volumes and limited range of feed sizes.
Wear Resistant Linings
In bulk material handling, the wear and tear within the conveyance apparatus is high. The use of wear resistant linings helps to reduce the wear and tear of the equipment. These wear resistant linings are usually made of alumina ceramic and basalt, with rubber composite materials. They are corrosion and temperature resistant. They can be used across multiple industries and are usually easy to apply on site. The wear resistant linings are resistant to abrasions from fine grain and particulate matter and have good mechanical properties like tensile strength and tear resistance.