demineralization process of water

Demineralization process of water:

Raw water cannot be directly used in the boiler, because it contains many mineral salts in the form of icons that are harmful to the boiler.

The mineral salts are classified into positive ions and negative ions'.

Positive ions are called cations and negative ions are called anions

cations  are calcium, magnesium, potassium, sodium

anions are bicarbonate, carbonate , chloride and nitrate

So these mineral ions must be removed from the water in order to increase the life of the boiler, efficiency of the boiler during operation. These minerals ions are removed by the ion exchange process.

In the ion-exchange process, the vessel will be filled with the ion exchange resin. There are two types of resin

i) Cation Exchange resin
ii) Anion Exchange resin

The cation exchange resin will release H+ ions in exchange for impure cation ions.
The anion exchange resin will release OH- ions in exchange for impure anion ions.






This resin must be regenerated after some time to remove the impure ions and bring back its Effectiveness.

Difference Between steam boiler and Steam Generator

Difference between a steam boiler and Steam Generator

Steam boiler:

 A steam boiler is a device which converts water to steam in the steam drum by boiling the water at subcritical pressure

Steam Generator

A steam generator is a device, which converts the water directly into steam in water wall without boiling the water at supercritical pressure 

Advantages of CFBC boiler Over AFBC boiler

1. CFBC boiler have High processing temperature due to high gas velocity through the system

2. Combustion temperature can be constantly maintained around 870 deg c. which result in minimal
    NOX formation

3.better turndown ratio in CFBC boiler compared to AFBC boiler

4. higher combustion Efficiency in CFBC boiler compared to AFBC boiler

5. combustion air supplied in CFBC boiler at a pressure of 1000-1500 MMWC where else in AFBC        boiler itis supplied at 2000-3500 MMWC

Boiler turn Down ratio & Combustion Efficiency in boilers

Boiler Turn down ratio in boiler means the ratio of Boiler capacity at Maximum Firing with fuel to Boiler capacity with Minimum Firing with Fuel before shutdown.

The Normal Turn around ratio will be 4:1

If the turnaround ratio is high on/ off cycle will be less and high energy savings can be obtained.

Combustion Efficiency:

Combustion Efficiency means how effectively the heat content in the fuel is converted to useful heat. If the combustion efficiency increases boiler efficiency increases

Latent super heater vs platen super heater vs pendant super heater

Super heater
Super heater is useful for increasing the cycle efficiency of the power plant. super heater converts the saturated steam that is generated from drum into super heated steam and is sent to turbine. Super heater increases the steam temperature by keeping the pressure constant. super heated steam are usually in the range of 540 deg Celsius.

Types of super heater:
Latent super heater: 
This super heater is placed at the back pass of the boiler. It gains heat through convection from flue gas. It is the primary super heater that heats the steam coming from the steam drum. It helps to remove the water carry over, hence the name latent.It is place in low temperature zone of furnace so it is also called as low temperature super heater. The steam from latent super heater passes to the platen super heater for further heating.

Platen Super heater:
platen is a vertical single loop placed in the furnace with many parallel tubes carrying steam. platen has set of closly packed tubes appearing like plate. they are place in the upper part of the furnance. they pick up heat enterily by radiation as it is placed in the furnace top.

The platen coils are place 600mm- 1000mm apart to avoid formation of ash build up.

with increase in steam flow the steam temperature from the platen super heater  decreases. and with decrease in steam flow  the steam temperature increases This is because at lower steam flow steam absorbs greater heat and becoming hotter at low load.

pendant Super heater:
Pendant super heater is a vertical or horizontal multi loop super heater placed in the convection section of boiler with one or many parallel tubes carrying steam. the pendant tubes are place with space. It is normally vertically hanged from top, but also can be found as horizontal. The heat transfer is by a combination of radiation and convection but predominantly by the latter. With increase in steam load the temperature of the steam increases.

both pendant and platen super heater are required in a boiler to get to attain high steam temperature needed.Their characters can complement each other to get a fairly constant temperature at all loads thus minimum attemperation is required. 

Geared variable speed coupling / Geared Hydrodynamic coupling

The principle:
The geared variable speed coupling combines the hydro dynamic coupling and Mechanica Gear in one compact unit.
The geared variable speed coupling controls the speed of the driven machine precisely, quickly.

Uses:
It is used to control the speed of the Driven Machine,Vary the power transmitted Reduce the power consuption, Increases the productivity of operation. Motor can start at no load

Design and function:
*The hydrodynamic geared coupling consist of double helical gear integrated in a housing with a split   horizontal body.
*The gear box is located before the hydrodynamica coupling.
*In hydrodynamic coupling there are two wheels, pump wheel abd turbine wheel. pump wheel is          conected to the drive machine. and the turbine wheel is conected to the driven machine.
*The pump wheel rotates at constant motor speed  and the turbine wheel rotates atvariable speed.
*Using the hydro dynamic principle the fluid is transmitted from the pump wheel to the turbine wheel at variable output speed.
*The scoop varies the coupling filling. The filling amount determines the power transmitted and the    speed of the driven machine.
*An actuator varies the speed of the scoop tube, in this way speed can be controlled.
*Working oil is supplied to the hydrodynamic coupling for varying the speed
*lube oil is supplied to the gear box.
*working and lube oil circuits are seperate.

The actuator is Electro hydraulic actuator for quick and precision operation of the scoop. A simple 4-20 MA is requires to control the scoop position.

The motor will start with no load conditions and smoothly accelerate even with machines with large moment of inertia. This happens because the hydrodynamic coupling is empty during the motor starting, so it seperates the motor from the driven machine so that the motor runs at no load condition.
starting the motor at no load conditions are important for equipments having large moment of inertia or with processes with initially large load.

Classification Steel Pipes and Tubes

Steel pipe & tubes are classified by the following methods:

1. Manufacture: Method Broadly Classified as Seamless & Welded.
• Seamless method is further classified as Hot Finished & Cold Drawn.  
• Welded are classified as ERW, SAW, CDW, SW, MMAW.
2. Steel Chemistry: Carbon steel, Alloy steel, Stainless Steel.
• Carbon Steel are further classified as low, Medium, high carbon, manganese steel.
• Alloy steel are further classified by composition of chrome & moly.
• Stainless steel are classified by their various composition of Nickel, crome, moly etc.   
3. End Use;
• Tubes are used to transferred heat load through its walls (Thickness) 
• Pipes are used to transfer heat loads through its Bore