MEMORANDUM 

TO: Portland Cement NSPS Docket 

FROM: Keith Barnett, USEPA/OAQPS/SPPD/MMG 

DATE: October 16, 2007 

SUBJECT: October 15, 2007, Meeting between US Environmental Protection Agency 

(EPA) and Mr. Peter Paone of FL Smidth Inc. 

Introduction and Objectives 

The purpose of the meeting was to obtain information on the cement kiln design factors 

that result in low nitrogen oxide (NOx) and carbon monoxide (CO) emissions. Most of 

the information discussed in the meeting is included in the presentation attached to these 

meeting notes. 

 

Meeting Participants 

Keith Barnett, USEPA 

Mike Laney, RTI (contractor to EPA) 

Peter Paone, FL Smidth, Inc. 

Information discussed in the Meeting 

FL Smidth is building the kiln for Drake cement in AZ and GCC in Pueblo CO. They are 

currently looking at mercury and total hydrocarbon abatement technology. 

There are two types of raw mill – vertical and ball mills. Vertical grinding is 50 percent 

more efficient that ball mill grinding. 

Loss on ignition in a cement kiln is 35 percent, mostly CO2. About 2-5 percent of the 

CO2 is left in the limestone after the calciner. 

Tertiary Air – air from the clinker cooler returned to calciner 

Primary air – burner air – this is the smallest air flow 

Secondary Air – clinker cooler air to kiln that enters under the clinker cooler 

Types of NOx 

Feed NOx – negligible 

Thermal NOx – formed in kiln, much larger amount, not formed in calciner, need 

at least 1300 o

C. 
Fuel NOx – formed primarily in calciner 

Cement kiln NOx is primarily NO (98 percent on average) 

Factor affecting formation of thermal NOx 

Max theoretical flame temperature 

Excess air rate 

Maximum materials temperature (burnibility) 

Flame shape (burner type) 

One percent or less of free lime left in clinker 

Hard materials require more heat to react 

The FL Smidth kiln burner has a small air annulus, shaping swirl air and axial air. The 

burner pipe length is 8 – 12 meters, maybe 1 meter in diameter. 

Their adjustments, how far the burner goes (in or out), swirl air, axial air. 

Factor that affect fuel NOx (calciner) 

Fuel nitrogen content 

Calciner design 

Temperature inside calciner 

There is a NOx reduction reaction that takes place in the calciner that reduces NOx 

formed in the rotary part of the kiln. This reaction is favored at higher calciner 

temperatures. 

Factor affecting CO emissions 

Calciner 

Fuel type 

Fuel fines 

Retention time 

Calciner design 

Raw Materials 

Organics in the raw materials 

Addition of fly/bottom ask (due to carbon in these materials) 

CO emissions can be as low as 0.5 lb CO/ton clinker with low excess air, and can be as 

high as 2-3 lb/ton clinker. 

2
3

About 95 percent of the FL Smidth calciners are the ILC design. In the SLC-D they add 

a precombustion chamber to the ILC. The SLC-D is for low volatile fuels and waste 

fuels. 

In their designs they try to produce a reducing condition at the bottom of the calciner to 

reduce NOx. Feed a low percentage of meal at the bottom (15 percent) and the rest at 

point(s) higher in the calciner. Tertiary air is used to complete combustion. 

The calciner temperature is limited to 1100 o

C to prevent materials from getting sticky. 

Retention time 0.1 to 0.15 seconds. 

Increased retention time and hot zones lower CO. 

From a NOx perspective petroleum coke is not a good precalciner fuel, but it is a good 

kiln fuel. 

Florida has a lot of problems with burnability because they have a lot if easy grinding 

limestone mixed with hard quartz, and high volatile coal. 

You need volatile coal and low nitrogen fuel to meet 1.95 lb/ton clinker in the long term 

without SNCR. If burring 100 percent pet coke you can get 2.8 – 3.3 lb NOx /ton clinker. 

The fineness of the pet coke is a big factor. 

SNCR does not increase CO emissions in FL Smidth systems. 

Lower NOx emissions prior to the SNCR system reduce SNCR system costs. 
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Telephone: 

202-566-1744 

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202-566- 9744 

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