[Terrapreta] Ammonia Scrubbing Technology, Issues of Hg and By Products of Coal Combustion

[dyarrow at nycap.rr.com]

given the unresolved questions about sequestering heavy metal 
contaminants (mercury, uranium, thorium, etc.) from exhaust gases from 
fossil fuel plants in charcoal, perhaps an interim strategy is to 
apply such flue gas scrubber charcoal by-product to forest soils 
rather than farm soils.  this allows study of the effects of scrubber 
char on soils and ecosystems without endangering food and feed 
producing farmland.  many forest soils are also badly in need of 
carbon-trace element-microbial recharge in order to boost growth rates 
and overall plant vitality.  forests are, after all, key components in 
the lungs of the planet, and need as much regeneration as farmlands.

david

----- Original Message -----
From: Shengar at aol.com
Date: Friday, March 16, 2007 11:36 pm
Subject: [Terrapreta] Ammonia Scrubbing Technology, Issues of Hg and  
By Products of Coal Combustion
To: terrapreta at bioenergylists.org

> 
> Ammonia Scrubbing Technology, Issues of Hg and other By products  
> of Coal 
> combustion
> 
> 
> I have been in contact with several chemical engineers, both 
> corporate and  
> government, that basically tell me that the TP/Ammonia scrubbing 
> technology  
> faces no practical hurdles. But when it comes to dealing with  the 
> fraction of 
> volatilized mercury up stream scrubbing will be necessary. The  
> non-volatile 
> uranium, thorium, fall out, and that radon also present  in coal 
> combustion  is 
> of no consequence for this process. 
> 
> Their general feeling is that direct liquidfaction and IGCC 
> approaches to  
> clean coal are complicated, expensive and except for pumping CO2 
> down oil gas  
> wells other deep geologic strata sequestration is untested ,  
> expensive  and 
> also limited in scope.
> 
> After a year of researching and running TP-Tech by way more 
> competent  folks 
> than I, in the many fields of study to which TP lends itself, I 
> have found  no 
> technological road blocks.
> 
> Injection of powdered activated carbon (PAC) into the flue gas is 
> currently  
> the front runner technology that is nearest commercialization for 
> mercury (Hg) 
> removal. The PAC needs to be further enhanced with halogens, like 
> bromine,  
> to be really effective with subbituminous coals such as Powder 
> River Basin  
> coals. The Hg-loaded dust is then removed with filter bags (bag 
> houses) or  
> electrostatic precipitators. A problem is that fly ash is 
> typically removed in  
> the same unit, thus resulting in fly ash containing extra carbon 
> (and Hg). That  
> carbon generally makes the fly ash useless as a concrete 
> amendment, thus  
> destroying by-product market value.
> 
> In high-sulfur bituminous coal combustion the Hg in generally in 
> ionic  form, 
> and can be removed by wet scrubbers . Use of wet scrubbers is 
> being  expanded 
> significantly to address mandated SO2 control, thus also achieving 
> a  
> simultaneous co-benefit of Hg removal. The potential downside is 
> the eventual  
> disposition of the Hg that shows up in the byproduct gypsum 
> obtainable from the  
> scrubber sludge. Workarounds are being looked at for these cases 
> above. 
> 
> There are a bunch of other approaches in various stages of  
> development. , 
> one patent pending, but still only at the laboratory  scale, where 
> the Hg is 
> captured within the material of the filter bags, thus  keeping the 
> Hg separated 
> from the fly ash. The Hg is disposed of with the old  bags at the 
> end of their 
> life, or recovered from the bag material at that  time.
> 
> Danny Day's process can be fitted at the end of any of the Hg 
> removal  steps, 
> though there would be little, if any additional removal credit for 
> NOx or  
> SO2.
> 
> 
>   
> 
> Erich J.  Knight 
> Shenandoah Gardens
> E-mail: shengar at aol.com
> (540)  289-9750
> 
> 
> 
> 
> 
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