Different Types Of Boilers । Boiler Operation And Operation Coefficient.
A boiler is a closed vessel or mechanical device by which water is converted into steam by the application of heat. Steam production is done as a carrier. Steam can easily transfer temperature and pressure from one place to another.
# Different Types Of Boilers:-
(A) Based on construction boiler are,
Fire Tube Boiler,
Water Tube Boiler.
(B) Based on the water circulation boiler are,
Natural Circulation Type Boiler,
Assisted Forced Type Boiler,
Forced Ones Through Type Boiler.
# Natural Circulation Type Boiler:-
In those boilers, the boiler water comes from the steam drum to the water drum with a down cammer and again from the water drum through the riser tube to the boiler water to the steam drum. In other words, in this case, water and steam are in the riser tube at the same time. Due to the density difference and the hot water wants to go up through the riser tube and manually water comes to the water drum with the down cammer. In a word, the water circulation in the boiler is due to the density difference, hence it is called Natural Circulation Type Boiler.
FEEDWATER→ DEAERATOR → F WATER PUMP → ECONOMIZER → ↓
↓ RISER TUBE ← MUD DRUM ← DOWN COMMER ← STEAM DRUM ↵
→ STEAM DRUM → SUPERHEATER.
# Assisted Forced Type Boiler:-
If the water circulation in a boiler comes down from the steam drum to a pump header and circulates from the pump header to the boiler with the required water supply through the pump to the boiler, the boiler is called Assisted Forced Circulated Type Boiler.
FEEDWATER→ DEAERATOR → F WATER PUMP → ECONOMIZER → ↓
↓ ← CIRCULATING PUMP ← DOWN COMMER ← STEAM DRUM ↵
→ MUD DRUM → RISER TUBE → STEAM DRUM → SUPERHEATER.
# Forced Ones Through Type Boiler:-
Once the through-type boiler is a single-tube boiler. Here the amount of water that is given in the tube evaporates completely and the water that is given only once i.e. the water that is given once is completely steamed out, it is called Forced Through Type Boiler.
This removes some of the highly concentrated impurities water or heavy water that remains in the boiler tube. Although it is a single tube, the construction of this tube is such that even if there is no water in the tube, the tube does not burn or damage and the superheated steam comes out from the boiler tube.
FEEDWATER → DEAERATOR → FEED WATER PUMP → ECONOMIZER → ↓
SUPER HEATER ←SUPER HEATER ← WATER SEPARATOR ← EVAPORATOR ↵
(C) Based on the application of heat boilers are,
Direct fire boiler,
Indirect fire boiler ( Waste Heat Boiler).
(D) Based on steam pressure boilers are,
Low-pressure Boiler < 20 Kg,
Medium-pressure Boiler < 40 Kg,
High-pressure Boiler > 40 Kg.
(E) Based on the critical point boiler are
Sub Critical Boiler,
Super Critical Boiler.
Total Heat Of Steam:-
Sensible Heat (100 KCal) + Latent Heat (539 KCal) = Total Heat (639 KCal)
# Critical Pressure Of Water/ Critical Temperature Of Water/ Critical Point Of Water.
If the temperature of the water is increased to normal pressure, then the temperature of the water does not rise after 100°C, then it is called latent heat but when water is not raised after 218 kg pressure and 374°C, then the water temperature does not rise. Then after an increase in the water pressure of 218 kg and a temperature of 374°C, the water temperature continues to rise at a proportional rate.
That is, 218 kg pressure is called The Critical Pressure Of Water. and 374°C temperature is called The Critical Temperature Of Water.
That is, the combined state at a pressure of 218 kg and a temperature of 374°C is called The Critical Point Of Water.
# Flue Gas:-
Flue gas is the burning of fuel in a boiler furnace in contact with oxygen or air. Boiler exit flue gas contains Co2, Co, N2, O2, etc. Boiler exit flue gas contains more than 2% of O2 for better combustion and 100% fuel burn.
# Saturated Point Of Steam:-
# Saturated Temperature = ³√P × 100
Total Heat Of Steam = (100 KCal) + Latent Heat (539 KCal)
= Total Heat (639 KCal)
The heat that we can measure or sense is called Sensible Heat and the heat that we cannot measure or sense is called Latent Heat.
Again, Total Heat Of Steam = S/H +L/H = S/H + 0 (At critical Point) = S/H
The temperature and pressure at which water evaporates are called the saturated point of temperature and pressure or it is called the saturated point of water i.e. this steam of this temperature and pressure is called saturated steam.
Again, the temperature or boiling point and the pressure at which the water is saturated are respectively called the saturated temperature and saturated pressure of that water. And it’s also called wet steam. It contains 2 to 5 percent of water.
# Superhit Steam:-
If Saturated steam is superheated by a superheater, then it’s called superhit steam. It is also called dry steam and superhit steam does not contain water molecules.
# Degree Of Superheat Temperature:-
The temperature required to make saturated steam superheat is called The Degree Of Superheat Temperature.
The Saturated Steam Temperature + Degree Of Superheat Temperature = Superhit Steam Temperature.
# The Ignition Temperature:-
The lowest temperature at which a fuel burn is called the ignition temperature of that fuel. For this, the fuel is taken to the ignition point by the ignition energy or ignition temperature.
# The Pilot Ignition/ Auto-Ignition:-
If the ignition temperature or the ignition point of the fuel in the combustion chamber is raised with the help of a pilot burner, then that process is called Pilot Ignition.
If the ignition temperature or at the ignition point, of the fuel in the combustion chamber is raised by any other source then that process is called Auto-Ignition.
# The Flammability Limit:-
The amount or proportion of air and fuel that is suitable for fuel burning is called The Flammability Limit of that fuel.
CH4 = LFL (5%) ∼ HFL (15%)
Air = 95 % ∼ 85 %
In this case, 5% CH4 with air is called The Lower Flammability Limit (LFL) of CH4 and 15% CH4 mixture with air is called The Higher Flammability Limit (HFL) of CH4.
CH4 : Air = CH4 – 97 %
CH4 + 2O2 → CO2 + 2H2O
21% O2 in =100% Air
1% O2 in = 100÷21 % Air
2% O2 in = (100×2)÷21 % Air
That is, in this case, Fuel: Air = 1: 9.52
This means that 9.52 % air must be given to each 01% CH4 or to react completely, but 9.52 × 1.1 = 10.46 % air is supplied to the furnace for 100% reaction of fuel with air, so that there is no shortage of oxygen in the furnace or flue gas.
That is, in this case, Fuel: Air = 1: 10.47 %
# 100% conversion in furnace depends on three factors:-
01. Complete mixture or Turbulent mixture.
# The Flashpoints:-
We know that when a liquid or solid is heated, the heating surface will be hit first, then vapor will form there, and then when the mixture of vapor and air reaches the proportional lower flammability limit, the object will flush and this is called the flushing point of the object. That temperature is called the flushing temperature of the object. The lower flammability limit of any fuel Is flashpoints.