### FLOW BALANCING REPORT

POT LINE 7

ALCOA ROCKDALE ALUMI NUM SMELTER

Rockdale, Texas

Table of Contents

1.0 Summary:

................................ ................................ ................................ 1

2.0 Instrument Validation:

................................ ................................ ............ 2

3.0 Flow Balance:

................................ ................................ ......................... 3

List of Exhibits:

Exhibit 1

– Flow Balancing Summary

Exhibit 2

– Raw DataAlcoa Rockdale Smelter Page 1

Flow Balancing Report

– Pot Line 7 050167AJ

The information contained herein is privilege and confidential information and is intended only for the use of the addressee’ s

co mpany. Any dissemination, distribution, or copying of this material to others, in whole or in part, is strictly prohibited w ithout the written permission of the CEO/Pres. of Air Control Science Inc. 

### 1.0 Summary:

Air Control Science , Inc. (ACS) was retained to flow balance the Line 7 pot fume collection system at Alcoa’s Rockdale Aluminum Smelter in Rockdale

T exas . ACS crews completed the balancing work May 13, 2005

.

The Line 7 fume control system consists of two separate scrubber systems, one located in the east courtyard, and one in the west courtyard. Each scrubber system

consists of 6 reactor modules and 6 fans

. The east courtyard system maintains draft on the east half of Line 7, pots 1 through 40 in rooms 128 and 130. The west courtyard system maintains draft on the west half of Line 7, pots 41 through 80 in rooms 128 and 130. Draft is controlled by parallel blade fan exhaust dampers, which are positioned based on a fan amp input.

Alcoa conforms to a regulatory emission limit as measured at potroom building

roof monitors , and has established an internal benchmark limit below the regulatory limit as a target maximum. Alcoa has experienced problems in previous years during summer months with measured emissions approaching internal target maximum limits , particularly from Line 7 and Line 8

. Alcoa’s objective in balancing pot draft is to reduce the ri sk of potroom emission excursions as measured at the building roof monitors.

Alcoa reports original design pot flows ranging between 3,200 ACFM and 3,500 ACFM for Line 7 and 8 pot draft. Prior to balancing, ACS measured pot flows ranging from 3,000 ACF M to over 4,000 ACFM. Prior to balancing, pot draft was found to average 3,150 ACFM for the east half of Line 7 and 3,350 for the west half of Line 7. During balancing, pot draft was adjusted to approximately 3,200 ACFM for the east half of Line 7 and 3, 300 ACFM for the west half of Line

7. Table 1 provides a summary of flow settings for each scrubber system.

Table 1 Flow Balance Summary

Scrubber System Pots Served Pre

- Balance Average Flow Post Balance

Average Flow

East Scrubber 1

- 40, rooms 128 and 130 3,150 ACFM 3,200 ACFM

West Scrubber 41

- 80, rooms 128 and 130 3,350 ACFM 3,300 ACFMAlcoa Rockdale Smelter Page 2

Flow Balancing Report

– Pot Line 7 050167AJ

The information contained herein is privilege and confidential information and is intended only for the use of the addressee’ s

co mpany. Any dissemination, distribution, or copying of this material to others, in whole or in part, is strictly prohibited w ithout the written permission of the CEO/Pres. of Air Control Science Inc. Because several pots at the east half of Line 7 required a 100% open damper setting to achieve target flows, it is believed that the selected target flow setting of 3,200 ACFM for the east half of Line 7 was maximized to match the east scrubber system capacity. It is believed that target flow setting for the west half of Line 7 could possibly have been increased to 3,350 ACFM to match the west scrubber system capacit y; however additional flow testing should be completed prior to attempting further adjustments to verify expected capacity gains.

Alcoa and ACS have previously recorded final damper position angle to establish a target setting when starting up a new pot . However, flow measurements for this balancing effort were successfully made using an averaging pitot tube that greatly simplifies the damper setting process. Further, pot flows were found to be very sensitive to minor adjustments in damper settings, ma king it difficult to measure and set dampers by angle. ACS recommends that Alcoa set dampers using the averaging pitot tube and velocity pressure setpoints identified herein when setting new pots in the future. The flow measurement and balancing procedur e used for this project is described in Section 3.



### 2.0 Instrument Validation : Prior to initiating flow balancing work, Alcoa requested that ACS validate suitability of an averaging pitot tube instrument similar to that used by the Alcoa Warrick facility. The averaging tube is a wand made of two hollow tubes, the upstream tube fitted with 4 total pressure holes on the leading edge, and the downstream tube fitted with a single static press ure opening in the center

- back of

the wand . Similar to a standard or “S” type pitot tube, velocity pressure is measured directly by an oil

- filled inclined manometer as the difference between total pressure and static pressure.

During validation, ACS measured flows at 13 pots using a standard pitot tube and

a 20

- point traver se at the 14” ID fiberglass duct , and using the averaging tube at a 3⁄4” half coupling port on the grounded, 15” ID aluminum duct . The 20

- point traverse was assumed to provide an accurate benchmark velocity pressure and flow, against which velocity pressure and flow as measured by the averaging tube was compared. C alculated flow as measured by the averaging pitot tube was adjusted by a constant to compensate for the following factors: averaging tube flow coefficient (reporte d by the manufacturer to be 0.63)

, andAlcoa Rockdale Smelter Page 3

Flow Balancing Report

– Pot Line 7 050167AJ

The information contained herein is privilege and confidential information and is intended only for the use of the addressee’ s

co mpany. Any dissemination, distribution, or copying of this material to others, in whole or in part, is strictly prohibited w ithout the written permission of the CEO/Pres. of Air Control Science Inc.

undeveloped flow in the ductwork caused by downstream elbow adjacent to measurement point

Flow measured by the averaging pitot tube was found to be accurate within 10%

of measured benchmark flow at a constant coefficient of 0.425. Table 2 provides a summary of instrument validation results.

Table 2

– Validation Data Summary

Measurement Point (Temp deg F) 20

- Point Ave.

VP (in. wg) 20 Point Flow

(ACFM) Averaging Tube

VP ( measured, in.wg) Averaging

Tube Flow (adjusted ACFM) Flow

Difference

28

- 80 (205) 0.54 3551 1.1 3816 266

28

- 79 (205) 0.61 3790 1.1 3816 27

28

- 70 (225) 0.47 3345 0.87 3445 100

28

- 64 (242) 0.41 3125 0.74 3216 91

28

- 65 (207) 0.67 3976 1.1 3822

- 154

30

- 80 (214) 0.51 3493 1.1 3842 349

30

- 79 (244) 0.48 3415 0.83 3411

- 4

30

- 76 (22 6) 0.69 4083 1.3 4216 133

30

- 73 (234) 0.64 3927 1.05 3811

- 115

30

- 72 (223) 0.67 4004 1.0 3690

- 314

28

- 70 (227) 0.45 3265 0.75 3203

- 62

28

- 65 (227) 0.59 3766 0.98 3632

- 124

30

- 76 (210) 0.70 4041 1.15 3917

- 124



### 3.0 Flow Balance:

To isolate impact from po t flow adjustments to one system, ACS focused balancing efforts on one scrubber system at a time. To coordinate work with Alcoa’s carbon setting shifts, ACS started balancing work on the west scrubber system during the day shift while carbon crews were wo rking on the east ends of the buildings . The east scrubber system was balanced during the swing shift when carbon crews were working on the west ends of the buildings.

Following instrument validation, ACS used the calibrated averaging pitot tube to

mea sure velocity pressure at all pots. For initial measurements, duct static

pressures were m easured at all pots, however were never found to deviate from

- 5 in. wg and therefore w ere not measured or recorded during flow balancing work.Alcoa Rockdale Smelter Page 4

Flow Balancing Report

– Pot Line 7 050167AJ

The information contained herein is privilege and confidential information and is intended only for the use of the addressee’ s

co mpany. Any dissemination, distribution, or copying of this material to others, in whole or in part, is strictly prohibited w ithout the written permission of the CEO/Pres. of Air Control Science Inc. Pot draft temperatur es were measured and recorded during each flow measurement and balancing effort except during balance iterations and final,

same

- day checking.

Working in 10

- pot manifold sections, ACS adjusted all dampers within a manifold to achieve a measured velocity pressure with in the target range. Depending on initial manifold flow conditions, one to two iterations were required on each pot to achieve desired balance distribution. If a few pots exhibited significantly higher flows than others, additional iteratio ns were likely required.

ACS began by measuring flow in pots 40 through 80 in both rooms 128 and 130

– the west scrubber system. Measured velocity pressures were tabulated and averaged by approximation to determine an appropriate balance set point. Fo r the west scrubber system, 0.78 ±0.03 in. wg was established as a target velocity pressure (as measured by the averaging pitot tube). Completing instrument validation and balancing the west half of Line 7 required one 5

- day period of 12 hour days

.

Follo wing balancing of the west scrubber system, ACS began work on the east scrubber system by measuring flow in pots 1 through 40 in rooms 128 and 130. Measured velocity pressures were tabulated and averaged by approximation to determine an appropriate balanc e set point. For the east scrubber system, 0.73 ±0.02 in. wg was established as a target velocity pressure. Completing balancing of the east half of Line 7 required one 3

- 1/2 day period of 12 hour workdays

.

Following balancing of each scrubber system, ACS completed random flow checks on roughly 10 pots per system, per room. All flow checks were found to be within original balance targets.

Some pots were found to have broken dampers or holes in fiberglass duct joints. Table 2 provides a summary of each defective or suspect pot

Flow Balancing is summarized on tables presented in Exhibit 2 of this report. Each exhibit contains a summary table and the raw field measurements.Alcoa Rockdale Smelter Page 5

Flow Balancing Report

– Pot Line 7 050167AJ

The information contained herein is privilege and confidential information and is intended only for the use of the addressee’ s

co mpany. Any dissemination, distribution, or copying of this material to others, in whole or in part, is strictly prohibited w ithout the written permission of the CEO/Pres. of Air Control Science Inc. The summary table is organized with the following rows and columns:

 Branc h of Main Duct Number

– is the section of duct in which the airflow measurement was taken. The numbers correspond to the node numbers on the provided drawings.

 Duct Diameter

– is the diameter of the duct in which the airflow was

measured.

 Gas Temperature

– is the temperature as measured in the duct, degrees F.

 Moisture Content

– not used.

 Humid Volume

– assumed dry air, see note on sheet.

 Static Pressure

– measured static pressure.

 Number of points on traverse

– total number of measurements made at the

location of the measurement.

 Pt

– point or location of measurement on duct

 VP

– measured velocity pressure

 Vel

– measured velocity

 Average Velocity

- is the average velocity measured in the duct.

 ACFM

– is the Actual Cubic Feet per Minute of airflow measu red in the

duct.

 DSCFM

– is the Dry Standard Cubic Feet per Minute of the measured airflow. DSCFM is the calculated airflow adjusted to standard conditions of air density (Dry air at 70 F and Sea Level).