power air quality factors and ratios

The following table provides cost and quantity factors and ratios which can be used for general analysis. These are critical to many important decisions made by utilities and their suppliers. They fit three categories. One is a need for an average rather than a specific case. The second is the usefulness of an empirical factor which may be more reliable than a calculated one. The third is a need for simplicity and speed which dictates use of an approximation rather than detailed calculations

We are providing a general forum for discussions of these factors. This forum will serve to provide useful additional information on the factors, change the factors, and add additional factors.

Many important decisions are determined by ratios or factors which are imprecise. In some cases there is no precise alternative. For example we list the cost of a new retrofit limestone system at $180/kW. There are many site specific variables which can raise or lower the cost. So even if we try to narrow the definition we can only improve the accuracy but by no means make it precise.

We could define these retrofits to include those where no fan upgrade or replacement is needed. This would eliminate one variable but there are many others. Also for many decision makers the need is for an average figure and not a number of specific figures

There are other factors which can be determined precisely but the cost and inconvenience of doing so outweighs the benefits. In these cases a rough average will suffice. The usage of coal at 3300 tons/yr/MW is far less precise than a detailed calculation which takes into account the ash in the coal, the efficiency of the combustor, and other variables. This is refined somewhat by also listing an average western coal at 3830 tons/yr/MW and average eastern coal 2900 tons/yr/MW.

There are some cases where an empirical factor can be more accurate than a carefully calculated one. We list lime consumption for dry scrubber systems at 45 tons/yr/MW in the Western U.S. but 80 tons in the East. Part of the difference is sulfur content but another part of the difference is the calcium in the flyash. More importantly the reactivity of the calcium in terms of surface area and other variables is also important. With so many variables which are difficult to identify it is better to use an empirical factor.

We encourage you to make comments about the listed factors, to suggest changes, or to add new factors which would be useful. Please reference a precise factor and give your name, affiliation and email contact. We will publish your comments in the “discussion” section for the factor. Please send these comments to editor@mcilvainecompany.com.

Category	Subject	Definition/Ratio	Quantity	Discussion
Coal	Heat- average	Btu/ton	20,268,000
Coal	Heat-western	Btu/ton	17,000,000
Coal	Usage-average	Tons/yr/MW	3333
Coal	Usage-eastern	Tons/yr/MW	2900
Coal	Usage-western	Tons/yr/MW	3830
Coal	Ash med S East Bitum	%	6.7
Coal	Ash- PRB	%	4.5
Coal	Bottom ash	% of coal	1.75
Coal	Flyash - average	Tons/yr/MW	233
Coal	Flyash typical	% of coal	7
Coal	Flyash - western	Tons/yr/MW	268
Coal	Flyash/bottom ash	ratio	4
Coal	Flyash/coal-eastern	Tons/yr/MW	203
Coal	Heat-eastern	Btu/ton	23,000,000
Coal	HHV PRB	Btu/lb	8750
Coal	HHV med S East Bitum	Btu/lb	13400
Coal	Moisture PRB	%	28
Coal	Moisture (med sulfur East Bitum)	%	6.4
Coal	Sulfur (med sulfur East Bitum)	%	1.6
Coal	Sulfur (PRB)	%	0.2
Coal	Sulfur lbs/mm btu	%	10,000/HHV
Coal	SO2 lbs/ mm btu	Sulfur lbs/ mm btu	*2
Coal	% S	SO2 lbs/mm btu	hhV/20,000
Coal	SO2 lbs/ mm btu	% S	20,000/hhv
FGD	Lime -dry scrub East	Tons/yr/MW	80
FGD	Lime dry scrub west U.S.	Tons/yr/MW	45	Discussion
FGD	Lime -wet	Tons/yr/MW	110	Discussion
FGD	Limestone system retrofit	$/kW	180
FGD	Limestone system - new	$/kW	140
FGD	Limestone-wet 2.5% S	Tons/yr/MW	195
FGD	Gypsum	Tons/ton of SO₂	2.8
FGD	Gypsum -2.5% S	Tons/yr/MW	320
FGD	Gypsum/lime	ratio	2.9
FGD	Gypsum/limestone	Ratio	1.64
FGD	Lime dry scrub East	Tons/ton of SO₂	1.4
FGD	Lime dry scrub West U.S.	Tons/ton of SO₂	1.1
FGD	Lime wet	Tons/ton of S0₂	0.95
FGD	Limestone calcium specification	% Ca	95
FGD	Limestone efficiency	%	95
FGD	Limestone wet	Tons/ton of SO₂	1.7
SCR	Catalyst cost China	$/ft³
SCR	Catalyst cost Europe	$/ft³
SCR	Catalyst cost U.S.	$/ft³
SCR	Catalyst replace or clean rate Europe/Japan	Interval-yrs	3
SCR	Catalyst replace or clean rate U.S.	Interval-yrs	1
SCR	Catalyst volume -honeycomb	Ft³/MW	34
SCR	Catalyst volume -plate	Ft³/MW	40
SCR	Efficiency	%	90