But if both are heated a little, than kerosene oil will catch fire and not wood.
This shows that ignition temperature of kerosene oil is lower than that of wood. Lets we the following activity which shows that a substance cannot bum until it reaches its ignition temperature. Booster 2 Why does the fire goes off when water is poured over burning wood? Explanation It happens because water absorbs a large amount of heat energy, which results in fall in the temperature of wood below its ignition temperature and the fire goes off. Test Yourself 1.
What do you mean by supporter of combustion? Name a gas which is a non-supporter of combustion. Ho do we control fire? We have seen homes, shops and factories caught in fire.
How can the fire be controlled from spreading? Generally, water is used to control fire. Water brings down the temperature of the combustible substance below its ignition temperature. The water vapour surrounds the combustible material, thus helping in cutting off the supply of air.
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So, that the fire is extinguished. Note: Fire produced by the burning of oil or petrol cannot be controlled by throwing water on it because water being heavier than oil, settles down the oil and oil continues to bum.? In the case of fires caused by burning liquid fuels, such as kerosene oil can be controlled by throwing sand or soil over it. We know that there are 3 conditions necessary for producing and sustaining combustion.
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Thus, fire can be controlled by removing one or more of these requirements of fire control. The fire extinguisher also try to cut off the supply of air or bring down the temperature of the fuel or both, to control the fire. The combustible substance as such cannot be eliminated in most of the cases from the place of fire. There are various types of fire extinguishers used for controlling a fire.
The job of a fire extinguisher is to cut off the supply of air or bring down the temperature of the fuel. To operate extinguisher Fig. Soda - acid fire extinguisher: Carbon dioxide liberated by the reaction of sulphuric acid with sodium bicarbonate solution comes out with a stream of liquid water at high pressure. Water puts off the fire by lowering the temperature of the combustible material below its ignition temperature and carbon dioxide cut off the supply of air to the combustible substance. Types of combustion Combustion is mainly of three types 1 Rapid combustion 2 Spontaneous combustion 3 Explosion 1.
Rapid combustion: The combustion in which the gas burns rapidly and produces heat and light is called rapid combustion. For example: When a burning matchstick is brought near a gas burner and the gas tap is opened, the gas immediately starts burning with the production of heat and light. Petrol, LPG, spirit, etc. Spontaneous combustion: The combustion in which no external heat is given is known as spontaneous combustion.
For example: Burning of white phosphorus in air. Difference between rapid and spontaneous combustion Booster 3 Forest fires are a result of which type of combustion and why? What are forest fires?
Why CO 2 is considered as the best fire extinguisher? Flame Look at the combustible substances around you and try to find whether on burning some of these materials given below forms a flame or not.
Flame: A region of burning gases is called flame.. A substance will burn with a flame, only if some gaseous substance is there to burn.
Booster 4 Why does a matchstick produce a flame on burning? Explanation When the matchstick catches fire or is burnt, the heat released due to the burning of chemicals on the match head, partly decomposes the wood to form wood gas. The wood gas then catches fire and produces a flame. Structure of a flame In order to understand the structure of a flame, light a wax candle and watch its flame.
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Carefully note the different coloured zones in the flame. Starting from the base of the flame, a flame has four zones. Vaporised wax gets oxidised to carbon monoxide and carbon monoxide bums completely with a blue flame in this zone. There is no burning in this zone. Burning hydrogen combines with oxygen to form water vapour.
Carbon also burns in this zone giving some luminosity to the flame and producing carbon dioxide. Some unbumt carbon particles are left which give rise to soot. It is the hottest part of the flame where complete oxidation burning of the fuel is taking place. Which one of the following is fuel of our body? Name the currency of energy in our by. Booster 5 Why do goldsmiths use the outermost zone of the flame for melting gold and silver? Explanation Goldsmiths, use the outermost zone or non-luminous part of the flame for melting or shaping gold and silver ornaments.
They direct the non-luminous part of the flame of candle on the gold with the help of a blow pipe. What is Fuel? Any substance which is easily available and burns in air at a moderate rate, producing a large amount of heat energy, without leaving behind any undesirable residue is called fuel. Example: wood, charcoal, petrol, kerosene, etc.
Booster 6 Why is sulphur not used as a fuel even though it can bum in air to produce heat? Explanation Sulphur is easily available in nature and can bum in air to produce heat.
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However, it is not a fuel because on burning, it forms a poisonous gas, SO 2 , which can cause serious respiratory problems and can even be fatal. Ideal Fuel There is probably no fuel that could be considered as an ideal fuel. We should look for a fuel which fulfils most of the requirements for a particular use. Classification of fuels On the basis of physical state, fuels are classified into three parts. Solid fuels: The fuels which occur In a solid state at room temperature are called solid fuels. Example: Wood, agricultural residues, charcoal, coal, coke, etc.
Liquids fuels: The fuels which occur in a liquid state at room temperature are called liquid fuels. Example: Liquefied hydrogen, petrol, oil, kerosene, diesel, etc. Gaseous fueils: The fuels which occur in a gaseous state at room temperature are called gaseous fuels. Example: Water gas, producer gas, coal gas, compressed natural gas CNG and gobar gas, etc. Fuel efficiency The amount of heat energy produced on completely burning one Kilogram of fuel in 02 is called the calorific value of a fuel. The more is the calorific value of a fuel, more is the efficiency of the fuel.
The calorific value of common solids, liquids and gaseous fuels is given below. Wet ESPs are less widely used and are primarily in hazardous-waste incineration applications. Dry ESPs operate above the dewpoint of the gas. Wet ESPs are constructed from materials that resist acid corrosion and operate under saturated-gas conditions. Dry ESPs are less effective than fabric filters for collection of submicrometer particulate matter 0. Their performance is influenced by a variety of design characteristics and operating conditions, including the number of electric fields used, charged electrode wire or rod and grounded collection plate or cylinder geometry, specific collection area ratio of collection surface area to gas flow rate , electrode design, operating voltage and current, spark rate, collector cleaning method to limit buildup or re-entrainment of dust , fluctuations in gas flow rate and temperature, particulate-loading fluctuations, particle-size distribution, and particle resistivity less important for wet ESPs.
Wet ESPs have superior submicron particle collection capabilities because they do not suffer rapping re-entrainment and dust layer back-corona problems associated with dry ESPs. In a properly designed unit, the important monitoring and process-control measures are inlet gas temperature dry ESPs only , gas flow rate, electrical conditions voltage, current, and spark rate , cleaning intensity and frequency, and hopper-ash level dry ESPs only. Wet inertial-impaction scrubbers, primarily venturi scrubbers, have historically been the particulate matter control technology of choice for most hazardous-waste and medical-waste incinerators.
They are inherently less efficient for submicrometer particulate matter than fabric filters or ESPs, but nonetheless can meet regulatory requirements in many applications.
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For injector venturi scrubbers, the corresponding criterion is liquid-nozzle pressure drop. Other important design and operating characteristics are the liquid-to-gas ratio, inlet gas temperature to avoid scrubber-liquid evaporation , solid content of recirculated scrubber liquid, mist eliminator efficiency, materials of construction to avoid corrosion and erosion, particulate loading, and particulate-size distribution.
In a properly designed unit, the most-important monitoring and process control measures are pressure drops, liquid and gas flow rates, and liquid blowdown rate blowdown is used to control solids buildup. A few designs use steam injection or scrubber-liquid subcooling to enhance flux force and condensation. For those designs, steam-nozzle pressure and scrubber-liquid temperature are additional useful monitoring measures. A commonly used APCD for removal of acid gases is a packed-bed absorber.