Rapid Mix Burner™ Case Study 103*Patented

U.S. Borax TODD Ultra Low EmissionsBurner Installation

The SituationIn November 1994, a TODD® Combustion

Rapid Mix Burner (RMB), utilizing induced Flue Gas Recirculation (FGR), was retrofittedinto a 21,500 lb/hr Nebraska boiler located atthe U.S. Borax facility in Wilmington, CA. TheRMB burner replaced an induced FGR burner permitted for 30 ppm NOx and 400ppm CO. The TODD retrofit consisted ofreplacing the existing burner and fan, andreusing the gas train and most of the controlsystem components. The objective was todemonstrate the RMB’s ability to operate atless than 9 ppm NOx and CO across the loadrange (5:1 turndown).

The BoilerA natural gas only, 26 MMBtu/hr RMB

was installed on a Nebraska model NS-B-35 watertube boiler rated for 21,500 lb/hr steam flow and equipped with an economizer.The burner installation included the RMB, aninduced FGR system and windbox baffles toprovide uniform air distribution to the burner. The characterizable fuel valve and air dampers

were physically linked to provide single-pointpositioning control over the air / fuel ratio acrossthe load range, while the FGR damper had a separate actuator and controller.

0 5 10 15 20 25 30

10

9

8

7

6

5

4

3

2

1

0

25

20

15

10

5

0

NOx ppm, O2 % FGR %

Load MMBtu/hr

NOx O2% FGR%

O2

NOx

FGR

CO < 3 ppm Over Load Range

Fig. 2: Borax Data

Fig. 1

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Developing Clean Air Solutions for Planet Earth®

The TODD ResultThe test results in fig. 2 illustrate the

burner performance with the boiler in automatic operation. The FGR rate varied fromabout 18% at low load to 25% at full load. TheNOx levels varied between 6 and 7 ppm overthe load range, while the CO varied from lessthan 1 ppm at full load to approximately 3 ppmat low load. The excess O2 varied from about4.5% at low load to 3.2% at full load.

The flame length was approximately 6-ftlong, and the flame was extremely stable acrossthe entire load range. There was no measurableimpact on the boiler’s efficiency. The burneroperates with a 6.5-in. draft loss and 5 psig gas pressure at full load. The RMB burner onthis boiler has been in operation sinceNovember 1994.

Third Party TestOn November 7, 1994, the boiler was

source-tested per SCAQMD protocol by theAlmega Corporation. The test results areshown below. The CO and NOx numbersare corrected to 3% O2.

Source Test Data

Load % O2 % CO ppm NOx ppm

25 3.4 3.0 8.2

53 2.6 0.9 7.1

98 2.7 0.1 6.8

John Zink Company, LLCTODD Combustion Group2 Armstrong Road, Third FloorShelton, Connecticut 06484 U.S.A.

800-225-0085 or +1-203-925-0380Fax: +1-203-925-0384www.toddcombustion.comwww.johnzink.com

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*Covered by one or more of the following patents:U.S. Pat. No. 5407347, 5470224

TODD COMBUSTION is a mark registered in the CTM countries.The abbreviated mark TODD is registered in the USA.

Copyright © 2003 by John Zink Company, LLC Printed in USA No. 34898-CS103