Know About Boiler Fundamentals Part-3
Today we discussed about a very important topic which is related to boiler familiarization that’s is Know About Boiler Fundamentals Part-3 in this article we discussed about lots of terms which is used into the boiler operation if anybody learn about it , its makes the things very easy to understand boiler operation as well as boiler maintenance also . boiler plays a very important role in modern electric generation units so every should know about it very well before operating it , a skilled full operator operate the boiler in efficient manner and also maximize the generation and reduced the generation cost . So these “Know About Boiler Fundamentals Part-3” helps the boiler operator become more skill-full and improving their knowledge in their relative field.
ECONOMIZER- economizer is a heat exchanger which utilize heat of exhaust flue gas from the boiler to increase feed water temperature, as the name suggest , Economizer is used to utilized the fuel economically or make the boiler economical. Hot exhaust flue gas from boiler which would have gone to atmosphere is used to increase the efficiency of boiler. This is a heat exchanger in which flue gas flow in a shell, arranged with water tubes. Heat of flue gas is utilized to increase the temperature of water to increase sensible heat of water. It is found by decreasing exhaust flue gases temperature by 16 deg. C , boiler efficiency increased by 1% . Also by increase feed water temperature by 6 deg.C ,boiler efficiency increase by 1 % .Uses the gases of combustion to heat the feed water.
Boiler Fundamentals Part-3
ELEMENT- A basic substance consisting of atoms. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions. Elements can only be changed into other elements using nuclear methods. An element is a substance whose atoms all have the same number of protons: another way of saying this is that all of a particular element’s atoms have the same atomic number.
ENTHALPY- Total heat in the steam. Enthalpy is a thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surrounding, symbolically enthalpy,H equals the sum of internal energy , E and the product of the pressure, P and volume V, of the system : H= E+PV
EROSION- Wearing away of metal caused by the wet steam. Erosion is a mechanical phenomenon and takes place due to process like friction, impact, turbulence etc. Due to abrasive combustion particles tube is eroded and it’s thickness reduces , which lead to failure of tube finally.
EQUALIZING LINE– Line used to warm up the main steam line and equalize the pressure around the main steam stop valve. In starting of the boiler we warm up the main steam line with help the equalizing line because of main steam line not get strained and thermal expansion of line is uniformly.
EVAPORATION TEST– Test that checks the operation of the low water fuel cutoff. evaporation test is very important test in this test boiler feeding cut off due to drum water level fall down to normal operating level . This evaporation test importance increase when the boiler in running condition due to any abnormalities boiler drum level is not maintained and boiler drum level get evaporated quickly in this conditions boiler fuel supply cut off and furnace temperature goes down and evaporation rate decrease . This evaporation test protects the boiler super-heater from get over heated.
EXCESS AIR- Air more than the theoretical amount of air needed for complete combustion of any fuel. Air contains 79% nitrogen and 21 % oxygen. Only oxygen is required for combustion. So it is required to handle large volume of air to get required quantity of oxygen. Large quantity of heat is required to heat this total air. So efficiency of the system decrease also if less air is supplied then complete combustion of combustible material may not take place. Excess air supplied can be measured by oxygen analyzer. Oxygen analyzer measured the oxygen percentage in flue gas. It should be monitored online for better control. Excess air monitored is done for efficient use of fuel. Some time co2 and co present in the flue gas is measured. The flue gas should contain co2 not co .It is to be kept in mind that excess air and excess oxygen are not same things. Air has roughly 21 % oxygen by volume, so 100% excess air is approximately equal to 10.5 % oxygen remaining at boiler exhaust stack.
EXHAUSTER– Discharges a mixture of coal and warm air to the burner. This coal is pushed through by nozzle with the help of primary air which is delivered by P.A fan. And hot air coming through the F.D which is called secondary air which mixes the coal inside the exhauster.
EXPANSION BENDS– Installed on boiler main steam lines to allow for expansion and contraction of the lines. All piping system expands and contract with change in temperature. Expansion of pipe depends on the expansion coefficient of piping material and temperature difference. Pipe line used in a boiler house carries hot fluid, so it must be allowed to expand. Pipeline is subjected to large variation in temperature during fluid flow and no flow “U” loops or expansion loops are provided in the pipe line to take care of this thermal expansion. This expansion loop allows piping system to absorb the force generated by expansion, without doing any harm to pipe line .expansion loop is provided at suitable interval. Expansion joints are used in low pressure pipe lines. Expansion bellow makes the pipe line flexible. It can take care of dimension change due to thermal expansion.
EXTERNAL TREATMENT- Boiler water treated before it enters the boiler to remove scale-forming salts, oxygen and no condensable gases. Feed water is treated externally before sent to boiler to eliminate hardness of the boiler water. Particularly in case of once through boiler, the feed water is treated externally to eliminate total hardness , as no further internal treatment is possible. There are some methods to remove the dissolved salts and minerals externally. Among them Demineralsing water treatment and reverse osmosis process are commonly used in steam generating plants. These two methods are discussed in subsequent section.
EXTRACTION STEAM– Steam that is extracted from a steam turbine at a controlled pressure for process. This extraction of steam is taken from the turbine different stages according to the temperature or pressure. This extraction of stem is called bleed. Bleed steam is used for the heating deaerator water or in other means like improving the quality of thread in cotton industry.
FEED WATER– Water that is supplied to the steam boiler. steam is formed in boiler from feed water. This water used in boiler is called as boiler feed water. Depending upon the source of water it contains different impurities. Before using the water in boiler these impurities are removed by various methods. Permissible level of impurities is different for different boilers. Feed water impurities are responsible for corrosion and scale formation in the boiler tube. Scale in the tune affects heat transfer. So the quality of feed water is responsible for higher life of boiler.
FEED WATER HEATER– Used to heat feed water before it enters the steam and water drum. In starting of the boiler feed water is heating with th help of PRDS steam after that turbine synchronization feed water is heating with the help of bleed steam if we increase the feed water temperature by 7 degree Celsius we increase the boiler efficiency upto 1% . Preheating the boiler feed water is also play an important role in fuel saving.
FEED WATER LINES- Lines leaving the open feed water pump and going to the boiler. These feed water lines are starting from the boiler feed pump which is connected to the deaerator it goes to the drum through economizer. In steam drum these lines goes for the bottom ring header through down comers. And again connected to the drum through the riser’s tube.
Know About Boiler Fundamentals Part-3
FEED WATER PUMP- Takes water from the open feed water heater and delivers it to the boiler at the proper pressure. This is critical equipment used in boiler house. Boiler feed pump supply deaerate and L.P dosed feed water to boiler. This pump has to pump feed water in to boiler drum against boiler drum pressure. So delivery pressure of this pump is higher than boiler drum pressure. Normally feed pump is a multistage pump, driven by electrical motor or turbine. In large boiler where steam generation capacity is more, more feed water is required to be supplied. In this case turbo feed pump can pump feed water in to boiler, utilizing steam of the boiler. So starvation can be avoided.
FEED WATER REGULATOR– Control used to maintain a normal water level that cuts down the danger of high or low water. Feed water from boiler feed pump is sent to boiler through feed water regulator or feed control valve. Normally there are two control valve. One is for low load and another is for higher load. One manual by pass valve is aslo provided for emergency. In some boiler both the control valve are capable for 100% load. Any one is selected for operation and another is kept in standby. Control valves are provided with two manual isolation valves at both sides for maintenance flexibility. The area where these valves are located is named as feed control station.
FEED WATER TREATMENT– Can be internal, using chemicals, or external, using water softeners. Protects boiler from scale and corrosion. These chemicals react with dissolved salts and converted them into sludge. This sludge can be removed from boiler water by blow down. Some salts are converted into less harmful sludge which can stay in boiler Water without creating any harm to boiler tube
FIELD-ERECTED BOILER- Boiler that must be erected in the field because of its size and complexity. this type of boiler is very complicated in erections because of during installation of boiler firstly a blue print is made before it starting after a blue print final drawing is are created after that according to the drawing concrete structure are setup after that all the boiler parts like boiler water wall panel, steam drum, economizer tubes are installation according to drawing with proper elevation. Afbc , cfbc , pf , traveling grate boiler are erected according to this procedure.
FIRE TUBE BOILER- Has heat and gases of combustion passing through tubes surrounded by water. In fire tube boiler hot flue gas flows inside the tube the tube is surrounded by feed water. The rate of steam generation in this boiler is less. As the flue gas flows inside the tube. Inside surface is exposed to flue gas. So for same number of tube, heating surface is less as compared to the water tube boiler. In these Boiler chances of explosions is less. But in case of explosion the risk of damage is very high.
FOAMING– Rapid fluctuations of the boiler water level that can lead to priming or carryover. Caused by impurities on the surface of the boiler water. Foaming is the formation of unbroken bubbles on the surface of the boiler water. The bubbles may be in thin layer, with few bubbles overlaying each other or it may build up throughout the steam space. As these bubbles burst, moisture is entrained with the steam. Some cause of foaming are
1. High dissolved solids concentration in the boiler water.
2. High suspended solid concentration
3. High alkalinity concentration
4. Oil and organic contamination in boiler water
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