Gravimetric Feeders

Overview

Demech has entered into technical collaboration with Hitachi Power Europe GmbH (HPE), Duisburg, Germany; to manufacture Gravimetric Coal Feeders. This gives Demech the unique advantage to supply Gravimetric Coal Feeders using the proven and reliable designs of Hitachi Power Europe GmbH.

HPE – a subsidiary of Hitachi, Ltd., designs and constructs fossil fired boilers for power generation. They have been the world class quality manufacturers of all the key components of such as utility steam generators, Environmental engineering, Turbines, Pulverisers, Ash Handling systems.

The major function of Gravimetric Coal Feeders is to continuously feed specified / required quantity of raw coal from the overhead bunkers to the coal pulveriser.

Technical Details
  • Gravimetric Coal Feeder manufactured by Demech is essentially a belt conveyor which measures the amount of coal, in terms of weight, being conveyed / fed to the pulveriser.
  • The feed rate is computed from load cell signal and belt speed signal collected from the load cells strategically mounted below the belt and the Hollow shaft sensor mounted on the tail pulley of the belt conveyor in the weigh controller.
  • The control and instrumentation features are achieved by combination of weigh controller, VFD and PLC-HMI housed in local & remote control panel.
Specifications

The three standard models manufactured by demech have the following basic specifications. However, using the same design platform, Demech can develop coal feeder with variations as per the requirement of customers.

Model GCF-1536 GCF-1026 GCF-0524
Operating Capacity Up to 150 t/h Up to 100 t/h Up to 50 t/h
Feeder Inlet Ø 36” (914 mm) Ø 26” (660 mm) Ø 24” (610 mm)
Belt width 1200 mm 1000 mm 800 mm
Belt speed variation Variable Frequency Convertor
Type of drives (Belt & CoC) Direct Shaft mounted geared motor
Weighing Accuracy ±0.5%
Design explosion pressure 350 kPa (g) as per NFPA 85
In-built safety features in form of alarm No coal on belt, Plugging in feeder outlet, High temperature in the feeder chamber, Belt loose etc.
Applications area
  • The primary application of Gravimetric coal feeder is for feeding coal to boilers.
  • However, it is used for any solid fuel feeding to boilers.
  • No pressure, NFPA 85 conditions or even higher pressure inside the coal feeder chamber can be variants in the design of feeders.
  • The primary function of Gravimetric coal feeder is to feed directly or indirectly solid fuel to the boiler at such a rate that is required by the boiler thus optimizing the fuel consumption.
  • The feeder also reports the total fuel consumption for a specified period which helps in calculating and controlling cost of power production.
Salient Features
  • The most prominent feature of Demech feeders is the load cell mounting arrangement which is bottom supported, pivot mounted cantilever frame. This arrangement makes it possible to use only one load cell for accurate load measurement unlike the side suspended two load cell arrangement.
  • This arrangement provides rigidity, easy alignment, protection against vibration & impact and has no effect of lateral forces due to the belt motion.
  • This also makes it possible to have low tension on the belt thereby increasing the life of the belt. Due to low belt tension, the feeder does not have the weigh down roller and the tail end roller also act as tensioning roller with external tensioning arrangement.
  • The belt has a unique continuous side wall with no cuts or opening which virtually eliminates coal spillage and does not allow any seepage of water to underside of belt.
  • The skirt liners cover the side walls from inside with their gap so adjusted to avoid any lodging of bigger coal particles between them.
  • The crowned drive pulley helps in centering the belt with addition of bottom V-guide further protects against belt slippage.
  • The motors are direct shaft mounted eliminating alignment activity.