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A cyclone furnace is a type of coal combustor commonly used in large industrial boilers. [1]
| | This article needs additional citations for verification .(December 2009) |
A cyclone furnace is a type of coal combustor commonly used in large industrial boilers. [1]
Developed in the early 1942 by Babcock & Wilcox to take advantage of coal grades not suitable for pulverized coal combustion, cyclone furnaces feed coal in a spiral manner into a combustion chamber for maximum combustion efficiency. [2]
During coal combustion in a furnace, volatile components burn without much difficulty. Fuel carbon “char” particles (heavier, less volatile coal constituents) require much higher temperatures and a continuing supply of oxygen. Cyclone furnaces are able to provide a thorough mixing of coal particles and air with sufficient turbulence to provide fresh air to surfaces of the coal particles.
Cyclone furnaces were originally designed to take advantage of four things
A cyclone furnace consists of a horizontal cylindrical barrel attached through the side of a boiler furnace. The cyclone barrel is constructed with water cooled, tangential oriented, tube construction. Inside the cyclone barrel are short, densely spaced, pin studs welded to the outside of the tubes. The studs are coated with a refractory material, usually silica or aluminium based, that allows the cyclone to operate at a high enough temperature to keep the slag in a molten state and allow removal through the tap. [1]
Crushed coal and a small amount of primary air enter from the front of the cyclone into the burner. In the main cyclone burner, secondary air is introduced tangentially, causing a circulating gas flow pattern. The products, flue gas and un-combusted fuel, then leave the burner and pass over the boiler tubes. Tertiary air is then released further downstream to complete combustion of the remaining fuel, greatly reducing NOx formation. A layer of molten slag coats the burner and flows through traps at the bottom of the burners, reducing the amount of slag that would otherwise form on the boiler tubes.
Cyclone Furnaces can handle a wide range of fuels. Low volatile bituminous coals, lignite coal, mineral rich anthracitic coal, wood chips, petroleum coke, and old tires can and have all been used in cyclones.
The crushed coal is fed into the cyclone burner and fired with high rates of heat release. Before the hot gases enter in the boiler furnace the combustion of coal is completed. The crushed coal is fed into cyclone burners. The coal is Burned by centrifugal action which is imparted by the primary air which enters tangentially and secondary Air which also enters in the top tangentially at high speed and tertiary air is admitted in the centre. Due to Whirling action of coal and air, a large amount of heat is generated (1500–1600 °C) and that covered the surface of cyclone and ashes are transformed into molten slag. The molten slag drained from the boiler furnace through a slag tap.
Coke is a grey, hard, and porous coal-based fuel with a high carbon content. It is made by heating coal or oil in the absence of air. Coke is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges.
A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.
A furnace, referred to as a heater or boiler in British English, is an appliance used to generate heat for all or part of a building. Furnaces are mostly used as a major component of a central heating system. Furnaces are permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water. Heating appliances that use steam or hot water as the fluid are normally referred to as a residential steam boilers or residential hot water boilers. The most common fuel source for modern furnaces in North America and much of Europe is natural gas; other common fuel sources include LPG, fuel oil, wood and in rare cases coal. In some areas electrical resistance heating is used, especially where the cost of electricity is low or the primary purpose is for air conditioning. Modern high-efficiency furnaces can be up to 98% efficient and operate without a chimney, with a typical gas furnace being about 80% efficient. Waste gas and heat are mechanically ventilated through either metal flue pipes or polyvinyl chloride (PVC) pipes that can be vented through the side or roof of the structure. Fuel efficiency in a gas furnace is measured in AFUE.
Fluidized bed combustion (FBC) is a combustion technology used to burn solid fuels.
A steam explosion is an explosion caused by violent boiling or flashing of water or ice into steam, occurring when water or ice is either superheated, rapidly heated by fine hot debris produced within it, or heated by the interaction of molten metals. Steam explosions are instances of explosive boiling. Pressure vessels, such as pressurized water (nuclear) reactors, that operate above atmospheric pressure can also provide the conditions for a steam explosion. The water changes from a solid or liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions, creating a danger of scalding and burning.
A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing.
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An air preheater is any device designed to heat air before another process, with the primary objective of increasing the thermal efficiency of the process. They may be used alone or to replace a recuperative heat system or to replace a steam coil.
Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel.
In a water boiler, draft is the difference between atmospheric pressure and the pressure existing in the furnace or flue gas passage. Draft can also be referred to as the difference in pressure in the combustion chamber area which results in the motion of the flue gases and the air flow.
A pulverized coal-fired boiler is an industrial or utility boiler that generates thermal energy by burning pulverized coal that is blown into the firebox.
A pulverizer or grinder is a mechanical device for the grinding of many different types of materials. For example, a pulverizer mill is used to pulverize coal for combustion in the steam-generating furnaces of coal power plants.
An oil burner is a heating device which burns #1, #2 and #6 heating oils, diesel fuel or other similar fuels. In the United States, ultra low sulfur #2 diesel is the common fuel used. It is dyed red to show that it is road-tax exempt. In most markets of the United States, heating oil is the same specification of fuel as on-road un-dyed diesel.
Tangential firing is a method of firing a fuel to heat air in thermal power stations. The flame envelope rotates ensuring thorough mixing within the furnace, providing complete combustion and uniform heat distribution.
A Wet-bottom furnace or wet-bottom boiler is boiler that contains a wet bottom furnace. It is a kind of boiler used for pulverised fuel firing. In wet bottom boilers, the bottom ash is kept in a molten state and tapped off as a liquid. Wet bottom boiler slag is the molten condition ash as it is drawn from the bottom of the slag-tap or cyclone furnaces. An advantage is the fact that the end product in this process has a higher value compared to that of a dry bottom boiler. Wet bottom boilers are preferred for low volatile coals that produce a lot of ash. But it has higher investment costs and higher maintenance costs, so it is built less often.
Recovery boiler is the part of kraft process of pulping where chemicals for white liquor are recovered and reformed from black liquor, which contains lignin from previously processed wood. The black liquor is burned, generating heat, which is usually used in the process of making electricity, much as in a conventional steam power plant. The invention of the recovery boiler by G.H. Tomlinson in the early 1930s was a milestone in the advancement of the kraft process.
Staged combustion is a method used to reduce the emission of nitrogen oxides (NOx) during combustion. There are two methods for staged combustion: air staged supply and fuel staged supply. Applications of staged combustion include boilers and rocket engines.
A coal burner is a mechanical device that burns pulverized coal into a flame in a controlled manner. Coal burners are mainly composed of the pulverized coal machine, the host of combustion machine control system, ignition system, the crater and others.
Computational fluid dynamics (CFD) are used to understand complex thermal flow regimes in power plants. The thermal power plant may be divided into different subsectors and the CFD analysis applied to critical equipment/components - mainly different types of heat exchangers - which are of crucial significance for efficient and trouble free long-term operation of the plant.
An industrial furnace, also known as a direct heater or a direct fired heater, is a device used to provide heat for an industrial process, typically higher than 400 degrees Celsius. They are used to provide heat for a process or can serve as reactor which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air. Heat is generated by an industrial furnace by mixing fuel with air or oxygen, or from electrical energy. The residual heat will exit the furnace as flue gas. These are designed as per international codes and standards the most common of which are ISO 13705 / American Petroleum Institute (API) Standard 560. Types of industrial furnaces include batch ovens, metallurgical furnaces, vacuum furnaces, and solar furnaces. Industrial furnaces are used in applications such as chemical reactions, cremation, oil refining, and glasswork.