Fixed Bed Combustion Of Coal Fired Power Plant

Fixed bed combustion is type of combustion system which is :
  • A continuous fuel feed system is  referred to as a stoker
  • Air flows up through the grate and through the bed of ash, char and fuel.
  • The tradition campfire is an example of fixed-bed combustion,
  • Widely use for coal, biomass and waste fuel 

(If you Want presentation file you can download in here "DOWNLOAD")

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Vivitar 28mm f2.8 Close focus Nikon Mount Review

Might be in the first of booming era , which is people using DSLR with manual lenses Vivitar lens is not quite famous yet. Vivitar is one  name of brand which is produced a lot of lenses with outstanding result.  In my opinion vivitar lenses has a good saturation color, sharp in wide open and you can get it in cheap price due to the ability of this lens produced a good image. Mine is 28mm f2.8 Close Focus nikon mount has a minimum focusing distance (MFD) 19 close enough to capture macro photography.

i picked up this picture from google

Here the data of the lens
  • manufacturer: Komine
  • filter: 49mm
  • markings: green meter scale
  • full focus range: 3/4 turn
  • aperture blades: 6
  • aperture range: f/2.8-f/16
  • maximum magnification: 1:5 (without MET)
  • maximum magnification with MET : 1:2
  • weight: 200g
  • diameter / length: 62mm / 36-43mm

First i bought this lens i doubt its ability to produce a good picture, but when i tried i would like to say "If you get cheap price, grab it with confidence, you wouldn't go wrong with this lens". Small lens, good ability for landscape, BW, even macro.

Here the example of pictures from this lens using Nikon D90

 Vivitar 28mm f2.8 close focus + D90 @f8

 Vivitar 28mm f2.8 close focus + D90 @f8

 Vivitar 28mm f2.8 close focus + D90 @f8

 Vivitar 28mm f2.8 close focus + D90 @f11 + MET

 Vivitar 28mm f2.8 close focus + D90 @f11 + MET

 Vivitar 28mm f2.8 close focus + D90 @f16 + MET

Those are the example pictures i taken with vivitar lens and my nikon camera, the choice is yours. But i highly recommended this lens due to its ability. :D 
ReadmoreVivitar 28mm f2.8 Close focus Nikon Mount Review

Download Template Presentasi Keren

Presentasi yang baik dan menarik merupakan salah satu kunci bahwa materi yang akan kita sampaikan lebih asik ketika disimak oleh audience bahkan dengan kemampuan powerpoint menyajikan presentasi bergambar membuat kita lebih interaktif. Ada banyak pilihan template, chart, diagram yang sudah ter install pada bawaan power point, namun sepertinya kurang cukup yah. Maka dari itu saya lampirkan link Download 15 file Template Presentasi Keren untuk di aplikasikan dalam presentasi tugas, project kerja dan sebagainya.

 Silahkan download disini :  15 template keren power point

Langkah membuat presentasi lebih menarik:

  1. Jangan terlalu banyak memuat teori sehingga tampak seperti koran, presentasi haruslah simple, jelas, dan mudah difahami.
  2. Perbanyak gambar pendukung dan chart diagram untuk membuat audience lebih nyaman memperhatikan presentasi kita.
  3. Selipkan video pendukung yang menarik.
  4. Gunakan template yang menarik sesuai dengan tema dan judul presentasi
  5. Kreasikan dengan ide kreatif anda sendiri. 

Selamat mencoba dan semoga sukses. 

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Feedwater Heater and Deaerator

I. Feedwater heater

A. What’s feedwater heater?
     Components in which fluid exiting the condenser is preheated by extracted steam from turbines  
B. Why feedwater heater?

o    To reduce thermal shock in boiler
    Thermal shock is a force that is caused by difference of expansion of solid (usually metals) because of  large difference of the temperature on its part
  1. Causes bending and cracking of the solid. Can be prevented/mitigated by 
  2. Reducing temperature difference (Applicable in this system)
  3. Using high conductivity materials (Applicable, but costly)
  4. Forcing the temperature increase/decrease to become gradual (not feasible
To reduce boiler load (except for startup phase)  = By preheating the  working fluid, fuel consumption is reduced 

     Disadvantages :
  1. More components, more initial cost, and more maintenance cost 
  2.  Steam bled from turbine is used to preheat the fluid instead of producing work, which in turn, decreasing the work output
  3. Adding components through which the fluid flows increase the loss by friction and heat loss to surrounding

Key consideration: Optimization of advantages 

C. What are the variations of feedwater heater?
 Open Feedwater heater
           Steam bled from turbine is allowed to mix with saturated water output of condenser.  

  1.  Faster heat rate between steam and saturated water, because of direct contact of both fluids 
  2. Direct contact heat exchanger is generally less expensive compared to other type (especially S&T HE), and easier maintenance process
  1.  Because of the pressure difference in all three state of turbine, condenser, and boiler, additional pump is required for each feedwater, which means, additional initial cost and maintenance cost

Closed Feedwater Heater
 Steam bled from turbine does not mix with saturated water output of condenser. In practice, shell and tube heat exchanger is commonly used

  1.  Fewer pumps required (only necessary in case of forward fed feedwater heaters). Because the non-direct contact heat exchanger, pressure difference between turbine and condenser is irrelevant
  2. Technology of S&T HE, which is commonly used in this case, is already mature, and still continue to develop

  1. Utilizing a steam trap valve, a throttling device that only allows liquid to pass. While cheaper and needs less maintenance than a pump, this device produce more irreversibility while producing no work. 
  2. HE used in this system (especially S&T type) is expensive, and the maintenance is not as easy as its direct contact counterpart  

Steam Trap
    When the steam enter the system (ex : closed feed water)  and heated the water inside pipe of CFW it will condenses and produce condensate and reduce heat contact area, we need remove it and need the valve to prevent leakage of steam

Steam traps are a type of automatic valve that filters out condensate (i.e. condensed steam) and non-condensable gases such as air without letting steam escape.

II. Deaerator

What's deaerator?
A device that is used to dissolved gasses from working fluid?


What’s the importance of using deaerator?
      It helps to prevent corrosion by removing, mainly, dissolved oxygen (main corrosive agent) and CO2 (secondary corrosive agent, by carbonic acid) Oxygen is removed until at most 7ppb (0.005 cm3/L). CO2 is usually completely removed)

How's deaerator work? 
    By heating the working fluid. Rate of dissolved oxygen released from the water is proportional to the temperature. At saturation temperature at a given pressure, almost all oxygen is released
                By adding oxygen scavenger (sodium sulfide (N2SO3) to Sodium sulfate (N2SO4))

Sodium sulfide is more reactive to oxygen compared to water. One of the disadvantages of this method is the sedimentation of sodium sulfate at the bottom of de-aerated water storage tank.

What are the variations of deaerator?

·         A. Tray type (Cascade Type Deaerator)
This type includes a vertical domed deaeration section mounted on top of horizontal cylindrical vessel which acts as de-aerated water storage tank.
The purpose of the cascaded trays within the deaeration section is similar to fill in cooling tower, which is to increase the heat transfer of water, which in turn, increasing the heat transfer rate. Boiler feedwater enters the deaeration section on top of the device; while heating steam enters through submerge pipes in the de-aerated water storage tank. As mentioned above, solubility of oxygen in the water decreases with increase of temperature.

B. Spray type
   The spray type deaerator consists only of a vessel that serves both as deaeration section and as de-aerated water storage tank.

In this type, instead of using trays to increase the heat transfer area, sprinkler nozzle is used. The main goal is still to increase the temperature of the boiler feedwater.
In both of these deaerator types, some things that need to be considered for choosing are :  
  • Price. Generally, tray type deaerator is more expensive and harder to design compared to spray type deaerator 
  • ·Efficiency. Efficiency of deaerator can be calculated by the same method of heat exchanger efficiency.  This depends on, among other thing, the size of the deaerator.
Some engineers also added vent condenser at the exit of the removed gasses, to filter some steam/water that might escape the deaeration process. This addition, of course, reduce the need of makeup water. 

ReadmoreFeedwater Heater and Deaerator


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