Re: Inactive Coal Stockpile Design Considerations
Dear Mr. Timm,
What is the width, length and height of the inactive stockpile. Whether it is triangular in cross section and linear type or is it radial type of stockpile.
Regarding black bituminous coal, as I understand, UK has the longest experience in handling this type of coal, and possibly coal authority in UK could be of help to you. This type of coal is being also extensively handled in India. Here, the general norms are as below.
1) Limit the stockpile height up to 10 m.
2) Spray the water on coal surface, by mechanized automatic method, so that there is no undue addition of water. This keeps the coal somewhat cooler and it also prevents dust emission by wind.
3) If there is too mucg risk of fire, then one should opt for the reclaiming mode which can enable the reclaiming of the coal surrounding the zone emitting fumes. The machine will reclaim the coal from the localised area but will not actually reach the subtle burning zone. Then, fire fighting people or the system sprays the water and puts off the subtle fire. As you know the spontaneous fire is generally without flame and its burning in the lower zone where there is build up of heat and lesser ventilation (and thereby lesser oxygen).
4) Although I have extensively dealt with the coal handling plants in power station (from OEM side), but I am not expert about the chemical engineering aspect of burning of coal such as
- If you cover the coal by tarpaulin, it will eliminate the ventilation. Will it not increase the chances of fire due to heat build-up. Contrary, the less ventilation also means less supply of oxygen, but this will come in play only when the actual fire has occurred. So, it seems covering by tarpaulin may be more conducive to start the fire. Regarding the covering by tarpaulin, if the stockpile is large, I have apprehension that it might get torn off in windy condition and will be difficult to manage / handle.
- Similarly, if you are covering whole surface by ash or other means, please think about its implications with respect to ventilation. Also, if the ash color is white (less black), then it will absorb less heat from the sun, and thereby lesser temperature of the coal within the stockpile.
5) The coal research institutes in India are located at Ranchi and possibly the engineers from there could be of more help with respect to factual information. The precautionary (preventive) measures as mentioned under serial # 1, 2 and 3 have been found to be adequate in India and we rarely come across / hear about the occurrence of serious type of such fires (damaging property or disrupting activity). .
I would also like to add that as I understand, this issue is more relevant to the hot climate countries and less relevant to country like UK, if coal storage is located in UK. In India one big power plant owner was very apprehensive about the spontaneous fire (may be due to higher calorific value of the coal etc). He specifically opted for side scraper-reclaimer machine so that machine could be immediately brought in position at the fuming zone, enabling quick reclaiming and exposure and thereby enabling quick remedial measure to put off the fire.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Author of Book : Belt Feeder Design and Hopper Bin Silo
Advisor / Consultant for Bulk Material Handling System & Issues.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 25882916 ■
Re: Inactive Coal Stockpile Design Considerations
Mr. Ishwar G Mulani,
I appreciate your knowledge on this subject and I should have made the location of the coal mine clearer. This exsisting coal mine is located in Queensland, Australia. Due to Queensland currently experiencing a drought, it is considered unsuitable to use water to cool the coal stockpile.
The stockpile is also triangular in cross-section and is approximately 100m long at the moment. The dimensions can change according to the design however the cross-section can't. Assuming that the stockpile maximum height is 10m (Angle of inclination of 15 degrees) then this would suggest that the stockpile would be 135m long to hold 50,000m3.
Reclaiming is currently performed by front end loader hence changing that equipment is not an option due to the expense involved.
I also have similar reservations regarding the covering of the coal sample with a tarpaulin, hence am now looking at compaction of the outer layer of the sample and then extensive temperature monitoring systems. In the event of a coal fire it will be detected soon before and procedure will be in place to protect the stockpile and prevent the fire from spreading.
Any further help in this matter is greatly appreciated.
Kind regards
Timm Schneider ■
Stock Pile
Greetings and salutations from the soon to be frozen eastern wilderness at 1140 feet above mean sea level,
Would not the simple solution be to break up the stockpile into smaller piles and in the end have an easier time firespotting?,
granted you have made your stock pile but it seems the lesser of two evils.
Granted you are low on H2O but baking soda, water and vinegar make a good firefighting compound if needed.
The idea is to eliminate hot spots in any firefighting scenario with any coal stock pile the potential is always there for hot spots and smouldering coal.
How far are you from accessable seawater? ■
Inactive Coal Stockpile Design Considerations
At the moment my company is considering options to cover the inactive coal stockpile to minimise the potential for coal fires. There seems to be a couple of options including covering the pile with a tarpaulin (plastic covering), spraying on a chemical or compacting it.
I have found some research from Spain that would suggest that ash/water slurry could be sprayed on to seal the stockpile. I am sceptical whether this sealant would be sufficient in keeping moisture out during rain periods. The other consideration that I had with the tarpaulin idea was that the coal would "sweat" under the plastic covering and only magnify the requirements of spontaneous combustion.
I am wondering what experience people have had when facing this problem and what design rules have been implemented to overcome this.
Kind regards
Timm ■