Vibrating Stoker Grate

Kinergy Vibrating Stoker Grate

Stoker Grate

Kinergy Vibrating Stoker Grate

The successful burning of ROM (Run-of-Mine) Coal to efficiently fire a Stoker Boiler has been achieved by a Kinergy Vibrating Grate. It was retrofitted under an existing stoker boiler in Southern Illinois. This 14 ft. (4.26 m) wide by 17 ft. (5.2 m) long Stoker Grate has been in productive use since 2007. It is electrically controlled to slowly move the coal combined with momentary “pulsing” to ensure the full depth is uniformly burning. This vibratory action consumes less than 3 HP (2.25 kW). The ROM Coal primarily being burned is the high sulfur, bituminous, stoker type which is 3” (75 mm) x 0” in size, which varies in “fines” content from about 20 to 50 percent, and it has changing moisture contents that typically vary from 8 to 15 percent. The heat value varies from 9,000 to 12,500 BTU’s per lb. This burning of ROM Coal is estimated to reduce the cost of this fuel by at least 15 percent, to as much as 60 percent. These attractive savings, combined with the many other benefits of this kind of Vibrating Grate, should help to make coal a more viable fuel.

While the purpose of this development was to burn ROM Coal, the same technology can be applied to other solid fuels that are inherently “dirty” or unclean. Examples would be wood waste, wood bark, municipal solid waste (MSW), refuse derived fuel (RDF), shredded rubber tires, shredded plants or scrub trees and the like.

Stoker Grate Photo 1

Fig. 1 – A drawing of the Vibrating Stoker Grate permanently retrofitted to an existing Boiler for burning ROM Coal

This patented Stoker Grate is usually installed horizontally and it is easily retrofitted under an existing Boiler. The top surface can be a water-cooled grate or it can be air cooled. The depth of the Grate assembly varies from 18” (457 mm) to 3 ft. (914 mm), which includes the multi-zoned air plenum located underneath. Both the water or air cooled grate and the air plenum are an integral part of this unit and vibrate with it. The vibratory drive configuration positioned under the air plenum requires 24” (608 mm) of height. The dynamic counterbalance is about 18” (457 mm) deep. The vertical standing isolation springs underneath the counterbalance allow the vibratory movement of the entire assembly. The vibratory motors are fitted under the counterbalance if needed. A floor mounted structural steel support can be used because all the ash is conveyed to the other end of the Grate. Therefore, any previously used ash hoppers are eliminated (Figure 1).

The incoming combustion air is distributed into zones that are independently adjusted in the plenum below the Stoker Grate. The counterbalance virtually eliminates any vibration transmission to the boiler or to the building.

The adjustable electrical control by means of a VFD (Adjustable Frequency) is used to automatically and repetitively vibrate the solid fuel at the wanted intervals to achieve the most efficient burning of the coal. The successful adaption of the Kinergy Drive to Stoker Grates makes the full range of adjustment from virtually zero to maximum possible.

Indications are that this Stoker Grate has availability for production. Other Stoker Grates that are reportedly called Traveling Grates normally don’t exceed 75%.

Design Features of the Kinergy Vibrating Stoker Grate

Kinergy has the most advanced vibratory machine technology available. Our design includes the following:

  • Durability:  Kinergy Vibrating Stoker Grates are built to last. The expected service life of the Kinergy Stoker Grate is 20 years or more.
  • Proven Performance:  The simple design and the best performance rating make the Kinergy Vibrating Stoker Grate the best choice. Particularly when so called “Dirty Fuels” must be burned.
  • Energy Efficiency:  All smaller or larger Stoker Grates utilize the Kinergy Drive System, which is the most versatile and energy efficient vibratory drive available. This drive is a combination of a free force (eccentric weights) input from an A.C. type electric motor with the output of sub-resonant tuned springs. When the applied load increases, the springs inherently drive harder. It maximizes the use of “Kinergy” which is defined as the kinetic energy developed by a spring’s motion during the drive portion of its cycle.
  • Flexible Connection:  This important sealing member with the Boiler’s combustion chamber is provided.
  • Self-Cleaning:  The Vibrating Grate is inherently self-cleaning of the solid fuel being burned and its resulting ash residue.
  • The Various Drive Configurations:
    • Underside Design:  The vibratory drive system is located underneath the feeding trough. This positioning is the most popular one for Kinergy Driven Stoker Grates.
    • End Drive Design:  The drive system is mounted on either end of the Vibrating Stoker Grate. This positioning has the advantage of a low profile type of design which minimizes head room requirements.
  • Eliminates the Pesty Ash Hoppers:  The vibratory conveying action collects all the burned ash, including the “siftings”, to the Grate’s discharge end and drops it into the awaiting appropriate containers.
  • Larger Dimensions:  Since the Kinergy Drive System spreads or distributes the vibratory, dynamic forces, the diameter or length and width dimensions are not restricted as they would be if concentrated at one grouping. Stoker Grate’s wider widths and longer lengths are available.
  • Simple Electrical Control:  By taking advantage of the inherent adjustable output, the Kinergy Vibrating Stoker Grate can have its operating stroke and frequency automatically and repetitively “pulsed”.
  • Reduced Sound Levels:  The Kinergy Vibrating Stoker Grate operates very smoothly and quietly, typically less than 80 dBA with or without load.
  • Low Maintenance:  By the use of components specifically designed to endure the vibratory action of the Stoker Grate, maintenance requirements have been markedly reduced.
  • Interchangeable Components:  Most of the component parts of the Kinergy Stoker Grate are interchangeable with other Kinergy Driven units even though their functions may differ. These common components extend to Vibrating Screens, Conveyors, Fluidized Bed Dryers and Coolers, Spiral Elevators, and the various types of special units. This reduces the number of spare parts required.
  • Counterbalancing:  All Kinergy Driven Stoker Grates are Dynamically “Counterbalanced”. This is inherent in their modern design.

The Kinergy Drive System has proven to be the most versatile and energy efficient one known for vibrating Induced Conveying machines. This makes Kinergy Vibrating Stoker Grates the optimal choice. To learn more about these innovative machines, please contact Kinergy at 502.366.5685 or kinergy@kinergy.com to request Kinergy’s ASME Power 2008 Technical Paper entitled “Burning Unprepared ‘Run of Mine’ Coal to Efficiently Fire a Stoker Boiler”.