Thermic Fluid Heater

Thermic Fluid Heater

In recent times, thermic fluid heaters have found wide application for indirect process heating. Employing petroleum - based fluids as the heat transfer medium, these heaters provide constantly maintainable temperatures for the user equipment. The combustion system comprises of a fixed grate with mechanical draft arrangements.

The modern oil fired thermic fluid heater consists of a double coil, three pass construction and fitted with modulated pressure jet system. The thermic fluid, which acts as a heat carrier, is heated up in the heater and circulated through the user equipment. There it transfers heat for the process through a heat exchanger and the fluid is then returned to the heater. The flow of thermic fluid at the user end is controlled by a pneumatically operated control valve, based on the operating temperature. The heater operates on low or high fire depending on the return oil temperature, which varies with the system load

The advantages of these heaters are:

• Closed cycle operation with minimum losses as compared to steam boilers.
• Non-Pressurized system operation even for temperatures around 250 0c as against 40 kg/cm2 steam pressure requirement in a similar steam system.
• Automatic control settings, which offer operational flexibility.
• Good thermal efficiencies as losses due to blow down, condensate drain and flash steam do not exist in a thermic fluid heater system.

The overall economics of the thermic fluid heater will depend upon the specific application and reference basis. Coal fired thermic fluid heaters with a thermal efficiency range of 55-65% may compare favorably with most boilers. Incorporation of heat recovery devices in the flue gas path enhances the thermal efficiency levels further.

 

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Fluidized Bed Combustion (FBC) Boiler

Fluidized Bed Combustion (FBC) Boiler

 

Fluidized bed combustion (FBC) has emerged as a viable alternative and has significant advantages over conventional firing system and offers multiple benefits – compact boiler design, fuel flexibility, higher combustion efficiency and reduced emission of noxious pollutants such as SOx and NOx. The fuels burnt in these boilers include coal, washery rejects, rice husk, bagasse & other agricultural wastes. The fluidized bed boilers have a wide capacity range- 0.5 T/hr to over 100 T/hr.

When an evenly distributed air or gas is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh, the particles are undisturbed at low velocity. As air velocity is gradually increased, a stage is reached when the individual particles are suspended in the air stream – the bed is called “fluidized”.

With further increase in air velocity, there is bubble formation, vigorous turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid particles exhibits the properties of a boiling liquid and assumes the appearance of a fluid – “bubbling fluidized bed”.

If sand particles in a fluidized state is heated to the ignition temperatures of coal, and coal is injected continuously into the bed, the coal will burn rapidly and bed attains a uniform temperature. The fluidized bed combustion (FBC) takes place at about 840 OC to 950 OC. Since this temperature is much below the ash fusion temperature, melting of ash and associated problems are avoided.

The lower combustion temperature is achieved because of high coefficient of heat transfer due to rapid mixing in the fluidized bed and effective extraction of heat from the bed through in-bed heat transfer tubes and walls of the bed. The gas velocity is maintained between minimum fluidisation velocity and particle entrainment velocity. This ensures stable operation of the bed and avoids particle entrainment in the gas stream.

 

Other Topics

IC engine,  Method of Ignition,  mechanical Engineering, English books,Photoshop tutorials,Harry potter,Best 100 english books,IC engine,Metal Casting,Mechnical Previous Years Gate Question Papers ,Mechanical-old-question-paper,Milling Quiz,Forging Quiz,Cold Extrusion,Hot Extrusion,CLutch,Wet Clutch,Introduction to Flywheel,Flywheel: FACTOR, Governors ,Thermal Power Plant,Pulverizer,Boiler,What type of boiler do you need?