Fluidized Bed Boilers
India has large reserves of Coal and with the Indian government going all out to offer coal blocks to private players and industries in the field of Power generation, Steel and Cement, it is expected that power industry in India will grow many folds. Since, most of the reserves are low grade coal with high ash content, it will be imperative that most of the power plants will use this low grade coal or rejects from coal washery as fuel. To utilize these fuels, AFBC boilers are the best solution and can be designed to fire coal rejects with high ash content alone or with a mix of fuels.
Also, due to their low flue gas temperature in fluidized bed which causes the reduction of NOx emissions as well as due to the addition of sorbent limiting the formation of sulfur compounds, fluidized bed boilers became an alternative solution for plants operating with conventional boilers.
The advantages of fluidized bed boilers
• Reduction of NOx emission - Combustion temperature 800 Deg C - 900 Deg C
• Reduction of sulphur oxides emission by ca. 90 - 95% - addition of sorbent to the furnace
• Possibility of firing with various low-grade solid fuels
• Operation of the boiler within the large range of load without auxiliary fuel
Basing on the engineering experience of Pressels Pvt Ltd, Hari Machines Ltd. has designed and delivered fluidized bed boilers. The construction of this type of boiler is simple and easy to maintain. The Company works also on biomass combustion in AFBC boilers. Hari Machines Ltd. has the right to use Pressels Private Limited (PPL) reference list and experience.
The AFBC Boilers are running successfully with multi fuel firing capability and recently in May 2006, 30 TPH Coal & Dolo Char (DRI Kiln waste) fired boiler with Steam Pressure 68 Kg/cm2 and Temperature of 485 Deg C was successfully commissioned in the state of Orissa, India.
The Boiler is a single drum design and is completely supported on the headers at the bottom. The fuel is fed below the bed coil into the fluidizing zone through a chute or chutes by means of secondary air. Combustion of fuel takes place in the fluidised state and the product flows through the boiler banks in four passes. A waste heat recovery system in the exit path of the flue gas, before it is discharged to the chimney through an induced draft fan, improves the thermal efficiency. First pass consists of furnace chamber made of membrane walls. Then flue gas goes to the second pass consisting of steam super heaters, third pass consisting of evaporative/generating banks and fourth pass consisting of economizer and tubular air heater. From the latter, flue gas is directed to the chimney through electrostatic precipitator and ID fans.