Yanche wrote: Berlin wrote:
NoSmoke wrote: guy and is from North Carolina so he is using bituminous data and not anthracite data.
The ash is the same. There's no magical and mystical difference to between anthracite and bituminous coal. Anthracite has lower volatiles because of the greater pressures exerted on it. That's about it as far as differences in composition.
They guys isn't using ANY sound data from anywhere if he's pissing himself over coal ash. What it contains isn't different than the dirt under your feet. The concentration of toxic trace elements aren't substantially different or more highly elevated than the soil in general. Coal ash hysteria is one more way for greenies to scare people away from coal - that's all there is to that hype.
But, isn't the collected fly ash from a power plant a concern? Think about it; many tons of coal are burned the fly ash is captured in a bag house or something similar. This concentrates the fly ash. Eventually the bag house needs to be emptied. Isn't it more hazardous now that it's concentrated? I would think so. That's why other minerals are added to the combustion fuel so that the resulting products of combustion, are less hazardous. It's all just a giant high temperature chemistry reaction. Yes, they use fly ash as a concrete ingredient, but isn't that just a method to bind the bad stuff so it can't harm the environment vs. putting it in a landfill where it might wash away. What am I missing?
I'm not sure what you're missing. Fly ash isn't hazardous waste either and although it occasionally tends to contain slightly different (higher or lower %) elements in itself -thus not NOT leaving them in the bottom ash, it really isn't different than most US soils either. If the flyash and the bottom ash were mixed, you'd have more or less the same concentrations of minerals and trace elements that you have in anthracite or bituminous ash from a home heating appliance. For example, typically coal is about 10% ash, thus when you burn coal, you end up with some elemnts/minerals entering the air and most inorganics staying with the ash - fly ash has about 10x the amount of uranium of the coal that was burned (slighly less with a small amount entering the air and a small amount staying in the bottom ash). http://pubs.usgs.gov/fs/1997/fs163-97/FS-163-97.html
In an industrial boiler with a powerful forced draft (and often pulverized fuel) you end up with certain things in the fly ash (vitrified light minerals) and heavier minerals and elements separate in the bottom ash - although there's a lot of overlap and it depends on the method and design of combustion. Some things are more concentrated in the flyash, but, not so substantially that it produces any dramatic or significant threat; obviously those that wish to scare everyone wish to skew things to make the great unwashed think so, but that's not really accurate for them to do and the facts speak for themselves. Fly ash isn't added to concrete to "bind it up" it's added because it is a very good portland cement replacement and it serves the duel use of disposal of a large amount of material as well as replacing a more costly material making it a smart economic decision.
Yanche, other 'minerals' are only added to the combustion process in a fluidized bed combustion furnace, In any various type of pulverized or stoker fired plant typically nothing is added to the combustion process but coal. There is after treatment of the exhaust gasses to "scrub" and remove sulfur and now mercury using various minerals and liquids, but typically limestone wet or semi-dry for SO2 reduction - this material is captured and not allowed to leave the stack.