Boiler Articles:

  1. Sample Combustion Calculations by weight method
  2. Boiler Efficiency calculations
  3. Sizing calculations of Boiler Pumps and ID / FD Fans 
  4. Sample Boiler Calculations

 

Sample Combustion Calculations by weight method

Combustion calculations are starting point for Boiler or any Thermal equipment design. Here is a sample calcualtion done for Coal with a calorific value of approximately 7200 Kcal/kg (12960 BTU/Lb).

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Boiler Efficiency calculations

Efficiency is a very important criterion in Boiler selection and Design. Efficiency figure depends upon the type of boiler as well as on the type of fuel and it’s constituents. For example, efficiency of a Bagasse fired boiler is about 70% where as that of oil fired boilers is about 85 %. Higher moisture content in Bagasse reduces it’s efficiency. So better criterion is efficiency based on LCV or NCV. This is widely used in Europe and efficiency based on HHV or GCV is used in other parts of the world. 

There are basically two methods to calculate efficiency of the boilers : Input-Output method and Heat Loss method. In Input-output method, boiler must be in steady running condition and the data of heat input in the form of fuel and air and heat output in the form of steam and other losses is taken.

Here we are going to discuss the second and more popular method. In this method, first we calculate the heat input. Then all heat losses are calculated. Effective heat output is heat input less the heat losses. Output to Input ratio gives the efficiency.

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Sizing calculations of Boiler Pumps and ID / FD Fans 

Sample sizing calculations for BFW pumps and Fans for a typical Coal fired Boiler generating steam of 50,000 Kg/hr at 67 kg/cm2 and 485 degC. (110,000 lb/hr at 950 PSI & 905 F). Feed Water inlet at 105 C and Exhaust gas temp at 150 C.

Let us first calculate heat load and fuel consumption of the above boiler. Pressure and temp at

1. Superheater Outlet : 67 Kg/cm2 & 485 C

2. Steam Drum : 73 Kg/cm2 & Saturated

3. Economizer inlet : Water inlet at 105 C

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Sample Boiler Calculations

Convert actual steam rating into From and At 100 C

Steam capacity from and at 100 C (212 F) is equivalent steam capacity if operating conditions are reduced to atmospheric pressure.

Steam capacity = 8000 kg/hr at 10.5 kg/cm2 saturated

Feed water inlet = 30 C

Heat load = 8000 (664-30) Kcal/hr

= 5.072e06 Kcal/hr = 20.127e06 btu/hr = 5.8976 MW

where Sat steam enthalpy = 664 Kcal/kg, Inlet water enthalpy = 30 Kcal/kg

Steam enthalpy at 100C and 1 atm pressure = 540 Kcal/kg 

Therefore, steam capacity F&A 100 C = 5.072e06/540 = 9392 Kg/hr

2. Heat Duty Calculations :

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