Vapour and Gas Power Cycles

Binary Vapour Cycle

In the binary cycle, two cycles with different working fluids are coupled series and the heat rejected by one being utilized in the other.

m = flow rate of binary in the necessary cycle per kg of steam cycle.

Brayton Rankine Combine Cycle Plant

In this cycle, the Brayton and Rankine cycles are combined to increase the efficiency.

When Plant in Series

Let us consider two cyclic pair plant coupled in series. The toppling plant operating on Brayton cycle and boiling are operating on Rankinee cycle

X_L = fraction of heat supplied which is loss 

When Plants Operate in Parallel

Where, 

Advantages of Combined Cycle

• High overall plant efficiency
• Low investment costs
• Great operating flexibility
• Water required in small amount
• Simplicity of operation
• Low environmental impact.

Proximate Analysis of coal

It indicates the behavior of coal when it is heated.

FC + VM + M + A = 100% by mass

FC = Fixed Carbon

Where, VM = Volatile Matter

M = Moisture

A = Ash

Ultimate Analysis of coal

It gives the chemical elements that comprise the coal substances, together with ash and moisture.

C + H + O + N + S + M + A = 100% by mass

Where, C = Carbon, H = Hydrogen,

O = Oxygen N = Nitrogen

S = Sulphur, M = Moisture,

A = Ash

Heating Value by Using Bomb Calorimeter

Heating value is the heat generated when the products of complete combustion of a sample of fuel are cooled to initial temperature of fuel air.

LHV = HHV – mw hfg

h_fg = Latent heat of vaporization

m_w = Mass of water vapour

m_w = M + gH + 𝛾_AW_A

where, M and H are the mass fractions of moisture and hydrogen in the coal. γ_A is the specific humidity of atmospheric air and W_A is the actual amount of air supplied per kg of coal.

Dulong and Petit Formula

If the ultimate analysis is known, the HHV of anthracite and bituminous coals can be determined approximately by using Dulong and Petit formula as

Where, C = Carbon, O = Oxygen, H = Hydrogen, S = Sulphur

Orsat Gas Analysis

Orsat gas analyser measures the volume or mole fraction of CO₂, CO and O₂ in the dry flue gas.

CO₂ + CO + O₂ + N₂ = 100% by volume

Height of Chimney

Height of chimney is given by following formula.

where, H = Height of chimney above the fire grate in metres

h = Drought pressure in mm of water

m = Mass of air used for per kg of fuel

T_a = Absolute temperature of air outside the chimney (K)

T_g = Absolute temperature of air inside chimney (K)

Condition for maximum discharge through the chimney.

The drought in mm of water column