sag/clinker in thermal power plant

Clinker and slag are the natural product of burning coal in furnaces. Which forms and where depend on furnace design and temperature. Most large steam plants let the clinker and slag melt and drain off into water where it breaks up into a frit that can be sluiced away to settling ponds for accumulation or disposal.

I worked in a 2400 MW station on the Ohio River near the coal fields. We took samples of the coal brought in by barges as we unloaded them. At times we would get coal that was more prone to slag. One method to utilize it was to mix it with the superior quality coal in the storage pile. We dealt with our clinker formation in several ways including shotgun shells, cold water spray, jackhammers. All this while in operation of a pressurized furnace.

i thank u for sharing your view on my question regarding clinker/slag. iam working in 210MW coal based power plant.it is tower type or single pass boiler.we have been facing problem of clinker formation in the boiler and at times clinker is falling in to the bottom ash scrapper conveyer and causing boiler trip on flame failure. our indian coal has 30% ash.

i would kindly want to know why clinker is forming and how it is causing trip in the boiler leading to flame failure.and what r the measures to avoid clinker formation.

b srinivas raju

Your problem of flame failure could be not due to clinker formation. If you have clinker formation(large fused mass), you will see it in bottom ash. Your problem could be due to dislodging of large mass of fly ash collected in SH and rH banks in first pass of boiler, obstructing the view of flamescanners. Load change can cause such ash dislodging.

HI,

Slagging is a factor of coal and is as an important factor as Cv. The reason I say this is that slagging and often takes units off. Blending coals can exacerbate the situation if due regard is not taken although some higher Cv coals will de-slag a boiler quicker than almost anything else. Routine slagging does occur around burners. These 'eyebrows' can not be easily removed but other areas can be partly de-slagged by correct operation of steam and water lances fitted to the boiler.

Depending on how important the issue of slagging is, I would suggest that tests are carried out on your coals for slagging propensity and you identify which of the coals you use has a tendency to slag and then you never burn them together.

Regards

Justin Humphrey

AIMechE

Slag buildup is a function of operating parameters of the furnace and certain fuel ash properties. Of specific interest is the ash fusion temperature, this is the point at which ash particles become plastic and begin sticking together. A sudden marked change in the slag-fouling characteristic of a furnace is probably due to a change in the fuel. You should require a proximate analysis for each train/boat load of fuel or on a daily bases, and an ultimate analysis at least annually of each mine that supplies fuel to your site. This data will help sort out fuel problems. Obtain the latest OEM operating parameters for the furnace and start talking to your plant operators. If the current operating parameters dare outside the OEM recommended operating parameters try to understand why the changes were made before making any new changes. If all else fails you can start the blind experimentation. Here is a short list of areas that could have some affect on slagging: Fuel preparation & coal fineness, primary/secondary air temperature, gross excess O2, overfire air, and finally systematically reduce the main steam (and Reheat) temperature setpoint to 90% of nameplate.