24-09-2014, 02:46 PM
ABSTRACT I underwent my training at KUDOS POWER PLANT of KUDOS CHEMIE LTD which is a manufacturer of a wide range of quality products like caffeine which is used as an ingredient in coke, tea, coffee. Kudos Chemie Ltd. (KCL) is a bulk drugs manufacturing plant located at village Kuranwala, Derabassi-Barwala Road, Derabassi, District Mohali, Punjab. The plant is already manufacturing Caffeine and Theophylline and is proposing to expand the manufacturing capacity of its existing bulk drugs, namely, Caffeine and Theophylline and start manufacturing of Theobromine, Aminophylline, Etophylline, bulk drugs. KCL also proposes to develop facilities for salt recovery as well as to generate 8 MW rice husk based power using steam turbine generator (STG) for meeting its additional power and steam requirements after the proposed expansion. It helped me to enhance my knowledge. I learnt many technical and problem solving techniques there in the plant. I was allotted with the project named as �TO INCREASE THE BOILER EFFICIENCY � I have worked on it with full dedication. I am v
8. PROJECT REPORT
8.1 TO INCREASE BOILER EFFICIENCY
8.1.1 CONCEPT OF BOILER
Aboilerorsteam generatoris, usually, a closed vessel made of steel. Its function is to transfer the heat produced by the combustion of fuel (solid, liquid or gaseous) to water, and ultimately to generate steam.
The steam produced may be supplied:
· To an external combustion engine (steam engines and turbines).
· To industrial process work in cotton mills, sugar factories, breweries at low
pressure.
· For producing hot water, this can be used for heating installations at much lower pressure.
8.1.2 TERMS FOR STEAM BOILER
· Boiler shell: It is made up of steel plates bent into cylindrical form and riveted or welded together. A boiler shell should have sufficient capacity to contain water and steam.
· Combustion chamber: It is the space, generally below the boiler shell, meant for burning fuel in order to produce steam from the water contained in the shell.
· Furnace: It is the space, above the grate and below the boiler shell, in which the fuel is actually burnt. The furnace is also fire box.
· Mountings: These are fittings which are mounted on the boiler for its proper functioning. They include water level indicator, pressure gauge, safety valve.
· Accessories: These are the devices which form an integral part of a boiler but are not mounted on it. They include superheated, economiser, feed pump.
· Grate: It is a platform in the combustion chamber upon which fuel is burnt. It is generally consists of cast iron bars which are spaced a part so that air can pass through them.
8.1.3 SELECTION OF A STEAM BOILER
· Power required
· Working pressure
· Rate at which steam is to be generated
· Geographical position of power house
· Available fuel and water
8.2 CLASSIFICATION OF BOILER
8.2.1 FIRE TUBE BOILER
In fire tube boiler the hot gases from the furnace pass through the tubes which are surrounded by water. It can generate steam only upto 24.5 bar. The rate of generation of steam is low upto 9 tonnes per hour. The floor area required is more i.e about 8 m^2 per tonne per hour of steam generation. Its overall efficiency is only 75 %. The transportation and erection is difficult. It can also cope reasonably with sudden increase in load but for a shorter period. The water does not circulate in a definite direction. The operating cost is less. The bursting chances are less. The bursting produces greater risk to the damage of the property. It is not suitable for large plants.
8.2.2 WATER TUBE BOILER
Awater tube boileris such kind of boiler where the water is heated inside tubes and the hot gasses surround them. This is the basicdefinitionof water tube boiler. Actually this boiler is just opposite offire tube boilerwhere hot gasses are passed through tubes which are surrounded by water.
ADVANTAGES OF WATER TUBE BOILER
· Larger heatingsurfacecan be achieved by using more numbers of water
tubes.
· Due to convectional flow, movement of water is muchfasterthan that of fire tube boiler hence rate of heat transfer is high which results into higher efficiency.
· Very high pressure in order of 140 kg/cm2can be obtained smoothly.
8.2.3 WORKING PRINCIPLE OF WATER TUBE BOILER
Theworking principle of water tube boileris very interesting and simple. It consists of mainly tow drums, one is upper drum called steam drum other is lower drum called mud drum. These upper drum and lower drum are connected with two tubes namely down-comer and riser tubes as shown in the picture. Water in the lower drum and in the riser connected to it, is heated and steam is produced in them which comes to the upper drums naturally. In the upper drum the steam is separated from water naturally andstoredabove the water surface. The colder water is fed from feed water inlet at upper drum and as this water is heavier than the hotter water of lower drum and that in the riser, the colder water push the hotter waterupwardsthrough the riser. So there is one convectional flow of water in the boiler system. More and more steam is produced the pressure of theclosedsystem increases whichobstructsthis convectional flow of water and hence rate production of steam becomes slower proportionately. Again if the steam is taken trough steam outlet, the pressure inside the system falls and consequently the convectional flow of water becomes faster which result in faster steam production rate. In this way thewater tube boilercan control its own pressure. Hence this type of boiler is referred as self controlled machine.
Another way to rapidly produce steam is to feed the water under pressure into a tube or tubes surrounded by the combustion gases. The tubes frequently have a large number of bends and sometimes fin to maximize the surface area. This type of boiler is generally preferred in high pressure applications since the high pressure water/steam is contained within narrow pipes which can contain the pressure with a thinner wall. It can however be susceptible to damage by vibration in surface transport appliances. In acast ironsectional boiler, sometimes called a "pork chop boiler" the water is contained inside cast iron sections. These sections are mechanically assembled on site to create the finished boiler.
The boiler suppliers and sales personnel will often cite various numbers, like the boiler has a thermal efficiency of 85%, combustion efficiency of 87%, a boiler efficiency of 80%, and a fuel-to-steam efficiency of 83%. What does these mean?
Typically,
· Thermal efficiency reflects how well the boiler vessel transfers heat. The figure usually excludes radiation and convection losses.
· Combustion efficiency typically indicates the ability of the burner to use fuel completely without generating carbon monoxide or leaving hydrocarbons unburned.
· Boiler efficiency could mean almost anything. Any fuel-use figure must compare energy put into the boiler with energy coming out.
· "Fuel to steam efficiency" is accepted as a true input/output value.
8.3 ELEMENTS ON WHICH EFFICIENCY VALUE DEPENDS
1) Boiler Stack Temperature: Boiler stack temperature is the temperature of the combustion gases leaving the boiler. This temperature represents the major portion of the energy not converted to usable output. The higher the temperature, the less energy transferred to output and the lower the boiler efficiency. When stack temperature is evaluated, it is important to determine if the value is proven. For example, if a boiler runs on natural gas with a stack temperature of 350°F, the maximum theoretical efficiency of the unit is 83.5%. For the boiler to operate at 84% efficiency, the stack temperature must be less than 350°F.
2) Heat Content of Fuel: The efficiency calculation requires knowledge of the calorific value of the fuel (heat content), its carbon to hydrogen ratio, and whether the water produced is lost as steam or is condensed, and whether the latent heat (heat required to turn water into steam) is recovered .
Disagreements exist on what is considered an "energy input". Unfortunately any fuel has two widely published energy contents. They are:
• The Higher Heating Value (HHV), also called Gross Calorific Value (GCV)
• The Lower Heating Value (LHV), also called the Net Calorific Value (NCV)
The gross calorific value (GCV) is the higher figure and assumes that all heat available form the fuel is to be recovered, including latent heat. In most equipment, this is not so the case, and the calculations of efficiency based on gross calorific value will give maximum obtainable efficiencies much lower than 100%, due to this irrecoverable loss.
Both the gross calorific value and net calorific value are equally valid, but for comparison purposes, a particular convention should be used throughout.
3) Fuel Specification: The fuel specified has a dramatic effect on efficiency. With gaseous fuels having higher the hydrogen content, the more water vapor is formed during combustion. The result is energy loss as the vapor absorbs energy in the boiler and lowers the efficiency of the equipment.
The specification used to calculate efficiency must be based on the fuel to be used at the installation.
4) Excess Air Levels: Excess air is supplied to the boiler beyond what is required for complete combustion primarily to ensure complete combustion and to allow for normal variations in combustion. A certain amount of excess air is provided to the burner as a safety factor for sufficient combustion air.
5) Ambient Air temperature and Relative Humidity: Ambient conditions have a dramatic effect on boiler efficiency. Most efficiency calculations use an ambient temperature of 80°F and a relative humidity of 30%. Efficiency changes more than 0.5% for every 20°F change in ambient temperature. Changes in air humidity would have similar effects; the more the humidity, the lower will be the efficiency.
8.4 EVALUATING BOILER EFFICIENCIES
EFFICIENCY= Eout/Ein
Where
• Eout is the energy needed to convert feed water entering the boiler at a specific pressure and temperature to steam leaving the boiler at a specific pressure and temperature. (This includes the energy picked up by the blow down and not converted into steam).
• Ein is the input energy into the boiler. The heat input is based on the high heat (gross calorific) value of fuel for efficiency calculations in US, UK and many other countries. Germany uses low heat (net calorific) value basis, implying that for an identical boiler, the stated efficiency will be higher.
There are two methods of assessing boiler efficiency;
1. Input – output or direct method, and