Any Instrument for Power Plant Coal Bunker/Silos

If you google vibrators coal material you will get information on vibratory systems that will prevent or loosen the blockage. These systems have been around for decades in the USA.

one example is this. http://www.navco.org/pneumatic_vs_cannon.html

Another possibility are fluidizers. They use compressed air to aerate the material. In some applications they work better than vibrators because vibrators can compact the material especially if you leave them on while material is not flowing. Just google fluidizers. A fluidizer would be a possibility in coal if the lumps are agglomerated fines and not agglomerated pieces.

If you have a moisture problem that is causing agglomeration you likely should fix this before trying other things.

Hi Both,

Thank you for your comment and they really help.

In fact, we also have vibrators for our coal bunker in power plant in China, but it seems blockage still happens due to coal quality, etc, which would still cause some big problem now and again.

So I wondered if any machine that have mechanical parts like a rod that put within/along the inner wall of coal bunker to loose the blockage if vibrators failed.

Thank you for your help

Paul

Consider air blasters (used for decades) or inserts for improved distribution. Mass flow of coal in bunkers is a specialized science (to prevent hangup or ratholing) and testing of coals for flow handling is a technological field of it's own. You need a consultant.

What is the blasting pressure used? The following method may be the crude one but can be tried if the problem is continuous.Arrangement of poking nozzles (inclined to the cone at the exit portion) to attend manually to the jamming problem at conical portion.

We use 100 psig (~7 bar) air from the plant's normal air system.

Rodding is a tried and true solution for jams consisting of larger chunks of coal, but it is less successful on fines, which are only slightly larger than grains of sand. At that size the particles tend to adhere to one another, particularly when wet. The rod will create a hole in the blockage, but not clear it.

1. An instrument called ' No coal flow detector' is available to detect the coal flow in the chute/duct from coal bunker/feeder. Flowing coal in chute/duct vibrates a rod inserted into the chute/duct continuously. When there is no coal flow, the vibration of pick up rod stops. 'Vibration' or 'no vibration' sensed by a electronic unit to indicate the 'coal flow' or 'no coal flow'

2. If the coal is flowing to the pulveriser/mill, the low value current to motor of pulveriser/mill can also indicate that coal is not flowing into the pulveriser/mill.

3. Differential pressure can measured across the pulveriser/mill. The low differential pressure across the pulveriser/mill will indicate that coal is not flowing into the pulveriser/mill.

R.Thiyagarajan

we have also used similar device called "auto-loose machine for coal bunkers", which I believe it is much better than the one you mentioned.

It uses hydraulic pressure as the drive force and put rods within the bunker to move upward & downward along the inner wall of coal bunker to achieve the objective of loose coal block. Just name some features of it here:

1). Machine would not work unless block happens. Once block happen, the machine would be activated and would get rid of the block within 18 seconds, then closed automatically.

2). Alarming automtically once loosing action failed.

3). User-friendly: could be operated in three modes say manually, presetting or automatically.

I believe this is the one that best meet your requirement.

Thank you for your attentionl.

Hello, rajant.

All of the devices you mention are good for monitoring free-falling material (although my personal experience with vibrating rods has been less that satisfactory). They are normally used between the metering feeder and the pulveriser, or at the pulveriser itself. Unfortunately, by the time a sensor at that location identifies a loss of flow, the operator has very little time (usually seconds) before the fuel flow to the furnace is disrupted. The problem posed by paulybg is above the feeder, where the coal completely fills the pipe. Since most blockages occur before the feeder, identifying a problem at this point gives the operator some time to try to fix the problem before the pulveriser runs out of coal and he loses flame in the boiler.

We use multiple sensors to look at flow through the entire process: the conveyor to the bunkers, from the bunkers to the feeders, from the feeders to the pulverisers and differential across the pulverisers for flow to the burners.

In the pipe between the bunker and the feeder we use 2 different types of sensors:

• The older type is a flat piece of steel ~40cm long, twisted into a spiral and suspended vertically in the pipe and free to rotate. A "speedometer cable" is attached to the top of the spiral. As the coal moves down through the pipe, the spiral is rotated. The other end of the cable actuates an optical encoder. If no pulses are received from the encoder over a 30 second period (indicating the spiral has stopped turning), the alarm sounds and the air blasters activate.
• The newer type uses microwaves to detect a change in the density of the material in the pipe. If the density drops by 50% (indicating that the coal is no longer tightly packed in the pipe), the alarm sounds and the air blasters activate.

"May anyone help advise if there are any device or equipment that could be used in coal-based power plant coal bunker/Silos, which could be used for lossing the blockage in the bunker and ensure the coal could enter the coal feed and to boiler."

Yes. Yes there is.