p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

20) ll-A-34 

Docket Number: 

A-88-02 

Printed 6/12/2008 10:28:49 AM Sheet 20 of 99 
P.2 

A-88-02 

United Sutes 

Environmenul Protection 

Agency 

Office of Air Quality 

Planning and Sundaids 

Reseaich Triangle Parle, NC 27711 

453/R-93-031 

July 1993 II A 3 4 

SE 

& EPA 

Technical Assessment of New 

Emission Control Technologies Used 

in the Hard Chromium Electroplating 

Industry 

NESHAP 

'•nzt&* 
SE-Q A n 

' 

7 > -

P.3 

EPA No. 453/R-93-031 

July 1993 

TECHNICAL ASSESSMENT OF NEW EMISSION CONTROL TECHNOLOGIES 

USED IN THE HARD CHROMIUM ELECTROPLATING INDUSTRY 

Prepared for: 

Industrial Studies Branch 

Office of Air Quality Planning and Standards 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 27711 

Prepared by: 

Midwest Research Institute 

Suite 350 

401 Harrison Oaks Boulevard 

Cary, North Carolina 27513 

July 31, 1993 

m B 
P.4 

NOTICE 

This report was prepared by Midwest Research Institute, 

Cary, North Carolina. It has been re-Viewed for technical 

accuracy by the Emission Standards Division of the Office of Air 

Quality Planning and Standards and approved for publication. 

Mention of trade names or commercial products is not intended to 

constitute endorsement or recommendation of use. 

11 

S 3 
P.5 

*. •''. T> 

PREFACE 

The Office of Air Quality Planning and Standards is 

responsible for establishing national;; emission standards for 

hazardous air pollutants. This document serves as a supplement . 

to Chromium Emissions from Chromium Electroplating and Chromic 

Acid Anodizing Operations--Background Information for Proposed 

Standards (BID), which provides technical support for the 

development of national emission standards for chromium 

electroplating operations. The information contained herein 

provides a detailed technical assessment of control technologies 

that have been demonstrated for use in the hard chromium 

electroplating industry since the BID was written. The 

assessment includes performance evaluations of each new control 

technology as well as the environmental and economic impacts 

associated with the use of the technologies. 

1 11 
P.6 

i I 

TABLE OF CONTENTS 

Page 

LIST OF FIGURES .-*/ vi 

LIST OF TABLES vii 

LIST OF ABBREVIATIONS xiv 

1.0 INTRODUCTION 1 

2 .0 BACKGROUND 2 

2.1 MESH- PAD MIST ELIMINATORS 2 

2.2 FIBER-BED MIST ELIMINATORS 3 

3.0 DESCRIPTIONS OF EMISSIONS CONTROL TECHNOLOGIES 4 

3.1 COMPOSITE MESH-PAD MIST ELIMINATOR SYSTEMS 5 

3.1.1 Composite Mesh Pads Used in Series 6 

3.1.2 Composite Mesh Pads Used in Conjunction 

with Packed-Bed Scrubbers 6 

3.2 FIBER-BED MIST ELIMINATORS 7 

4.0 EMISSIONS TEST DATA 8 

4.1 COMPOSITE MESH-PAD TESTS 9 

4.1.1 Mesh-Pad Mist Eliminator--Precision 

Engineering, Seattle, Washington 9 

4.1.2 Mesh-Pad Mist Eliminator--Monroe Auto 

Equipment, Hartwell, Georgia 16 

4.1.3 Packed-Bed Scrubber/Mesh-Pad Mist 

Eliminator System--Remco Hydraulics, 

Inc., Willits, California 21 

4.1.4 Discussion of Composite Mesh Pad 

Performance 31 

4.2 FIBER-BED MIST ELIMINATOR TESTS--NAVAL AVIATION 

DEPOT, ALAMEDA, CALIFORNIA 38 

4.2.1 Process Description 38 

4.2.2 Air Pollution Control 40 

4.2.3 Process Conditions During Testing 43 

4.2.4 Results of Emissions Testing 43 

4.2.5 Discussion of Fiber-Bed Mist Eliminator 

Performance 45 

4.3 SUMMARY OF EMISSION TEST RESULTS 49 

5.0 ENVIRONMENTAL AND COST IMPACTS 51 

5.1 AIR POLLUTION IMPACTS 51 

5.2 ENERGY IMPACTS 7 53 

5.3 WASTEWATER IMPACTS 57 

5.4 SOLID WASTE IMPACTS 57 

5.5 MODEL PLANT COST IMPACTS 60 

5.5.1 Mesh-Pad Mist Eliminators with Mesh Pads 

in Series 60 

5.5.2 Packed-Bed Scrubber/Mesh-Pad Mist 

Eliminator System 63 

5.5.3 Fiber-Bed Mist Eliminators 63 

iv 
P.7 

TABLE OF CONTENTS (continued) 

Page 

5.6 SUMMARY OF ECONOMIC IMPACTS 64 

6 .0 CONCLUSIONS/SUMMARY 67 

7.0 REFERENCES 69 

APPENDIX A. SUMMARIES OF EMISSIONS TEST DATA AND PROCESS 

OPERATING PARAMETERS A-1 

APPENDIX B. BASIS FOR THE DEVELOPMENT OF MODEL PLANT 

COSTS FOR NEW EMISSION CONTROL TECHNOLOGIES. B-1 

APPENDIX C. SUMMARY OF MODEL PLANT CAPITAL AND ANNUALIZED 

COSTS FOR NEW EMISSION CONTROL TECHNOLOGIES. C-l 

6 
LIST OF FIGURES 

P.8 

Page 

Figure 1. 

Figure 2. 

Figure 3. 

Figure 4. 

Figure 5. 

Figure 6. 

Figure 7. 

Figure 8. 

Figure 9. 

Figure 10. 

Figure B-1 

Figure B-2 

Schematic of the ventilation and control 

system at Precision Engineering, Seattle, 

Washington 11 

Schematic of control system at Remco 

Hydraulics, Inc., Willits, California 25 

Outlet chromium concentration data for 

composite mesh-pad mist eliminator systems 33 

Composite mesh-pad mist eliminator data -

inlet versus outlet concentrations 35 

Composite mesh-pad mist eliminator data -

efficiency versus inlet concentration 36 

Composite mesh-pad mist eliminator data -

efficiency versus inlet mass rate 36 

Schematic of a typical fiber-bed mist 

eliminator 41 

Fiber-bed mist eliminator outlet 

concentrations 46 

Fiber-bed mist eliminator outlet 

concentrations without high test values... 48 

Performance data for mist eliminator 

systems 50 

Plan view and ductwork specifications for 

the small hard chromium plating model 

plant B-27 

Plan view and ductwork specifications for 

the medium and large hard chromium plating 

model plants •. . . . B-28 

vi 
LIST OF TABLES 

P.9 

Page 

TABLE 1, 

TABLE 2 

TABLE 3a. 

TABLE 3b. 

TABLE 4. 

TABLE 5. 

TABLE 6. 

TABLE 7 

TABLE 8a. 

TABLE 8b, 

TABLE 9, 

DIMENSIONS AND OPERATING PARAMETERS FOR THE 

HARD CHROMIUM PLATING"'TANKS AT PRECISION 

ENGINEERING, SEATTLE, WASHINGTON 10 

AVERAGE OPERATING PARAMETERS MONITORED DURING 

EACH EMISSION TEST RUN AT PRECISION 

ENGINEERING, SEATTLE, WASHINGTON 14 

PERFORMANCE DATA FOR THE MESH-PAD MIST 

ELIMINATOR AT PRECISION ENGINEERING, 

SEATTLE, WASHINGTON (TOTAL CHROMIUM TEST 

RESULTS) 15 

PERFORMANCE DATA FOR THE MESH-PAD MIST 

ELIMINATOR AT PRECISION ENGINEERING, 

SEATTLE, WASHINGTON (HEXAVALENT CHROMIUM 

TEST RESULTS) 15 

AVERAGE OPERATING PARAMETERS MONITORED DURING 

EACH EMISSION TEST RUN AT MONROE AUTO 

EQUIPMENT, HARTWELL, GEORGIA 19 

PERFORMANCE DATA FOR THE MESH-PAD MIST 

ELIMINATOR AT MONROE AUTO EQUIPMENT, 

HARTWELL, GEORGIA 20 

DIMENSIONS AND OPERATING PARAMETERS FOR THE 

SEVEN HARD CHROMIUM PLATING TANKS AT REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA 23 

AVERAGE OPERATING PARAMETERS MONITORED DURING 

EACH EMISSION TEST RUN AT REMCO HYDRAULICS, 

INC., WILLITS, CALIFORNIA 27 

PERFORMANCE DATA FOR THE PACKED-BED SCRUBBER/ 

MESH-PAD MIST ELIMINATOR SYSTEM AT REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA 

(TOTAL CHROMIUM TEST RESULTS) 29 

PERFORMANCE DATA FOR THE PACKED-BED SCRUBBER/ 

MESH-PAD MIST ELIMINATOR SYSTEM AT REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA 

(HEXAVALENT CHROMIUM TEST RESULTS) 29 

PERFORMANCE DATA FOR COMPOSITE MESH-PAD MIST 

ELIMINATORS 32 

vll 

8 
P.10 

LIST OF TABLES (continued) 

TABLE 10. CHROMIUM ELECTROPLATING^ AJJD CHROMIC ACID 

ANODIZING TANK SPECIFICATIONS AT THE NAVAL 

AVIATION DEPOT, ALAMEDA, CALIFORNIA 

TABLE 11. PERFORMANCE DATA FOR THREE SCRUBBER/FIBER-BED 

MIST ELIMINATOR SYSTEMS AT THE NAVAL 

AVIATION DEPOT, ALAMEDA, CALIFORNIA 

TABLE 12. PARAMETERS FOR THE HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS 

Page 

39 

44 

52 

TABLE 13. HEXAVALENT CHROMIUM EMISSION ESTIMATES 

ASSOCIATED WITH THE USE OF PACKED-BED 

SCRUBBERS AND NEW EMISSION CONTROL 

TECHNOLOGIES AT HARD CHROMIUM ELECTROPLATING 

MODEL PLANTS 54 

TABLE 14. ANNUAL ENERGY REQUIREMENTS ATTRIBUTABLE TO THE 

USE OF PACKED-BED SCRUBBERS AND NEW 

EMISSION CONTROL TECHNOLOGIES AT HARD 

CHROMIUM PLATING MODEL PLANTS 55 

TABLE 15. SOLID WASTE IMPACTS ASSOCIATED WITH THE USE OF 

PACKED-BED SCRUBBERS AND NEW EMISSION 

CONTROL TECHNOLOGIES AT HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS 59 

TABLE 16. CAPITAL COSTS OF SINGLE PACKED-BED SCRUBBERS 

AND NEW TECHNOLOGIES FOR NEW AND EXISTING 

HARD CHROMIUM ELECTROPLATING MODEL PLANTS. 61 

TABLE 17. NET ANNUALIZED COSTS OF SINGLE PACKED-BED 

SCRUBBERS AND NEW TECHNOLOGIES FOR NEW 

AND EXISTING HARD CHROMIUM ELECTROPLATING 

MODEL PLANTS 62 

TABLE 18. ESTIMATED PERCENT CHANGE IN HARD CHROMIUM 

ELECTROPLATING COST OF THREE END PRODUCTS 

ATTRIBUTABLE TO VARIOUS CONTROL 

TECHNOLOGIES 66 

TABLE 19. ESTIMATED CHANGE IN PRICE OF FINAL PRODUCTS 

ATTRIBUTABLE TO THE INCREASE IN HARD 

CHROMIUM ELECTROPLATING COSTS WHEN USING 

VARIOUS CONTROL TECHNOLOGIES 68 

TABLE. A-1. SUMMARY OF EMISSIONS TEST DATA-- PRECISION 

ENGINEERING, SEATTLE, WASHINGTON. MESHPAD MIST ELIMINATOR - INLET A A-2 

v m 
LIST OF TABLES (continued) 

p.11 

Page 

TABLE A-2 

TABLE A-3. 

TABLE A-4. 

TABLE A-5. 

TABLE A-6 

TABLE A-7. 

TABLE A-8 

TABLE A-9 

TABLE A-10 

TABLE A-ll. 

TABLE A-12. 

TABLE A-13 

SUMMARY OF EMISSIONS TEST DATA--PRECISION 

ENGINEERING, SEATTLE;" WASHINGTON. MESHPAD MIST ELIMINATOR - INLET B A-3 

SUMMARY OF EMISSIONS TEST DATA--PRECISION 

ENGINEERING, SEATTLE, WASHINGTON. MESH--PAD 

MIST ELIMINATOR OUTLET A-4 

SUMMARY OF EMISSIONS TEST DATA--MONROE AUTO 

EQUIPMENT, HARTWELL, GEORGIA. MESH-PAD MIST 

ELIMINATOR INLET, WITHOUT FOAM BLANKET A-5 

SUMMARY OF EMISSIONS TEST DATA--MONROE AUTO 

EQUIPMENT, HARTWELL, GEORGIA. MESH-PAD MIST 

ELIMINATOR INLET, WITH FOAM BLANKET A-6 

SUMMARY OF EMISSIONS TEST DATA--MONROE AUTO 

EQUIPMENT, HARTWELL, GEORGIA. MESH-PAD MIST 

ELIMINATOR OUTLET, WITHOUT FOAM BLANKET A-7 

SUMMARY OF EMISSIONS TEST DATA--MONROE AUTO 

EQUIPMENT, HARTWELL, GEORGIA. MESH-PAD MIST 

ELIMINATOR OUTLET, WITH FOAM BLANKET A-8 

SUMMARY OF EMISSIONS TEST DATA--REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA. 

SCRUBBER/MESH-PAD MIST ELIMINATOR - INLET A. A-9 

SUMMARY OF EMISSIONS TEST DATA--REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA. 

SCRUBBER/MESH-PAD MIST ELIMINATOR - INLET B. A-10 

SUMMARY OF EMISSIONS TEST DATA--REMCO 

HYDRAULICS, INC., WILLITS, CALIFORNIA. 

SCRUBBER/MESH-PAD MIST ELIMINATOR OUTLET A-ll 

SUMMARY OF EMISSIONS TEST DATA--NAVAL AVIATION 

DEPOT, ALAMEDA, CALIFORNIA. LINE G 

FIBER-BED MIST ELIMINATOR OUTLET A-12 

SUMMARY OF EMISSIONS TEST DATA--NAVAL AVIATION 

DEPOT, ALAMEDA, CALIFORNIA. LINE L 

FIBER-BED MIST ELIMINATOR OUTLET A-13 

SUMMARY OF EMISSIONS TEST DATA--NAVAL AVIATION 

DEPOT, ALAMEDA, CALIFORNIA. LINE M 

FIBER-BED MIST ELIMINATOR INLET/SCRUBBER 

OUTLET A- 14 

ix 

10 
P.12 

LIST OF TABLES (continued) 

Page 

TABLE A-14 

TABLE B-1. 

TABLE B-2. 

TABLE B-3. 

TABLE B-4 

TABLE B-5 

TABLE B-6 

TABLE B-7. 

TABLE B-8 

TABLE B-9 

TABLE B-10, 

TABLE B-11, 

SUMMARY OF EMISSIONS TEST DATA--NAVAL AVIATION 

DEPOT, ALAMEDA, CALIFORNIA. LINE M 

FIBER-BED MIST ELIMINATOR OUTLET A-15 

PARAMETERS FOR THE HARD CHROMIUM ELECTRO- .. 

PLATING MODEL PLANTS B-29 

ANNUAL OPERATING COST FACTORS FOR MESH-PAD 

MIST ELIMINATORS, PACKED-BED SCRUBBERS/ 

MESH-PAD MIST ELIMINATOR SYSTEMS, AND 

FIBER-BED MIST ELIMINATORS B-30 

CAPITAL AND ANNUALIZED COST DATA SOURCES FOR 

MESH-PAD MIST ELIMINATORS, PACKED-BED 

SCRUBBERS/MESH-PAD MIST ELIMINATOR SYSTEMS, 

AND FIBER-BED MIST ELIMINATORS B-31 

CAPITAL COST ESTIMATES PROVIDED BY VENDOR C 

FOR MESH-PAD MIST ELIMINATORS WITH MESH PADS 

IN SERIES B-32 

CAPITAL COST ESTIMATES OF MIST ELIMINATORS 

WITH MESH PADS IN SERIES B- 33 

ESTIMATED ANNUALIZED COSTS OF MIST 

ELIMINATORS WITH MESH PADS IN SERIES B-34 

ESTIMATED CAPITAL COSTS OF MESH-PAD MIST 

ELIMINATOR UNITS FOR NEW AND EXISTING HARD 

CHROMIUM PLATING MODEL PLANTS B-35 

ESTIMATED ANNUALIZED COSTS OF MESH-PAD MIST 

ELIMINATOR UNITS FOR NEW HARD CHROMIUM 

PLATING MODEL PLANTS B-36 

ESTIMATED ANNUALIZED COSTS OF MESH-PAD MIST 

ELIMINATOR UNITS FOR EXISTING HARD CHROMIUM 

PLATING MODEL PLANTS B-37 

CAPITAL COST ESTIMATES PROVIDED BY VENDORS A 

AND C FOR PACKED-BED SCRUBBER/MESH-PAD MIST 

ELIMINATOR SYSTEMS B-38 

CAPITAL COST ESTIMATES OF PACKED-BED 

SCRUBBER/MESH-PAD MIST ELIMINATOR SYSTEM 

(VENDOR A) B-39 

@ 11 
P.13 

TABLE B-12 

TABLE B-13. 

TABLE B-14 

TABLE B-15. 

TABLE B-16. 

TABLE B-17. 

TABLE B-18. 

TABLE B-19. 

TABLE B-20. 

TABLE B-21. 

TABLE C-l. 

TABLE C-2. 

LIST OF TABLES (continued) 

Page 

ANNUALIZED COSTS OF PACKED-BED SCRUBBER/MESHPAD MIST ELIMINATOR SYSTEM (VENDOR A) B-40 

ESTIMATED CAPITAL COSTS OF PACKED-BED 

SCRUBBER/MESH-PAD MIST ELIMINATOR SYSTEMS 

FOR NEW AND EXISTING HARD CHROMIUM PLATING * 

MODEL PLANTS (VENDOR A) B-41 

ESTIMATED ANNUALIZED COSTS OF PACKED-BED 

SCRUBBER/MESH-PAD MIST ELIMINATOR SYSTEMS 

FOR NEW HARD CHROMIUM PLATING MODEL PLANTS 

. (VENDOR A) B-42 

ESTIMATED ANNUALIZED COSTS OF PACKED-BED 

SCRUBBER/MESH-PAD MIST ELIMINATOR SYSTEMS 

FOR EXISTING HARD CHROMIUM PLATING MODEL 

PLANTS (VENDOR A) B-43 

CAPITAL COST ESTIMATES PROVIDED BY MONSANTO 

ENVIRO-CHEM AND CECO FILTERS, INC., FOR 

FIBER-BED MIST ELIMINATORS B-44 

ESTIMATED CAPITAL COSTS FOR FIBER-BED MIST 

ELIMINATORS N. B-45 

ANNUALIZED COSTS OF FIBER-BED MIST 

ELIMINATORS B-46 

CAPITAL COSTS OF FIBER-BED MIST ELIMINATORS 

FOR HARD CHROMIUM PLATING MODEL PLANTS B-47 

ANNUALIZED COSTS FOR FIBER-BED MIST 

ELIMINATORS FOR NEW HARD CHROMIUM PLATING 

MODEL PLANTS. B-48 

ANNUALIZED COSTS FOR FIBER-BED MIST 

ELIMINATORS FOR EXISTING HARD CHROMIUM 

PLATING OPERATIONS B-49 

CAPITAL COSTS OF SINGLE PACKED-BED SCRUBBERS 

FOR HARD CHROMIUM ELECTROPLATING MODEL 

PLANTS C-2 

ANNUALIZED COSTS FOR SINGLE PACKED-BED 

SCRUBBERS FOR NEW HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-3 

XI 

12 
P.M 

LIST OF TABLES (continued) 

Page 

TABLE C-3 

TABLE C-4 

TABLE C-5 

TABLE C-6 

TABLE C-7, 

TABLE C-8. 

ANNUALIZED COSTS FOR SINGLE PACKED-BED 

SCRUBBERS FOR EXISTING HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-4 

CAPITAL COSTS OF MESH-PAD MIST ELIMINATORSWITH MESH PADS IN SERIES FOR HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-5 

ANNUALIZED COSTS FOR MESH-PAD MIST ELIMINATORS 

WITH MESH PADS IN SERIES FOR NEW HARD 

CHROMIUM ELECTROPLATING MODEL PLANTS C-6 

ANNUALIZED COSTS FOR MESH-PAD MIST ELIMINATORS 

WITH MESH PADS IN SERIES FOR EXISTING HARD 

CHROMIUM ELECTROPLATING MODEL PLANTS C-7 

CAPITAL COSTS OF PACKED-BED SCRUBBER/MESH-PAD 

MIST ELIMINATOR SYSTEMS FOR HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-8 

ANNUALIZED COSTS FOR PACKED-BED SCRUBBER/MESHPAD MIST ELIMINATOR SYSTEMS FOR NEW HARD 

CHROMIUM ELECTROPLATING MODEL PLANTS C-9 

TABLE C-9. ANNUALIZED COSTS FOR PACKED-BED SCRUBBER/MESHPAD MIST ELIMINATOR SYSTEMS FOR EXISTING 

HARD CHROMIUM ELECTROPLATING MODEL PLANTS... C-10 

TABLE C-10. 

TABLE C-11 

TABLE C-12 

CAPITAL COSTS OF FIBER-BED MIST ELIMINATORS 

FOR HARD CHROMIUM ELECTROPLATING MODEL 

PLANTS C-11 

ANNUALIZED COSTS FOR FIBER-BED MIST 

ELIMINATORS FOR NEW HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-12 

ANNUALIZED COSTS FOR FIBER-BED MIST 

ELIMINATORS FOR EXISTING HARD CHROMIUM 

ELECTROPLATING MODEL PLANTS C-13 

xi 1 

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P.15 

ABBREVIATIONS USED IN THIS DOCUMENT 

A 

Ah 

°C 

cm 

Cr03 

dscf 

dscm 

°F 

ft 

ft2 

ft3 

g 

gal 

gr 

hr 

hp 

in. 

in.2 

in. w.c. 

kg 

kPa 

kW 

kWh 

L 

lb 

lbf/ft 

m 

m

2 

m

3 

mg 

mil 

min 

MW 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

= 

-

= 

= 

= 

= 

= 

= 

ampere 

-., '/ ampere-hour 

degrees Celsius 

centimeter 

chromium anhydride, commonly known as 

dry standard cubic foot 

dry standard cubic meter 

degrees Fahrenheit 

foot 

square foot 

cubic foot 

gram 

gallon 

grain 

hour 

horsepower 

inch 

square inch 

inches of water column 

kilogram 

kilopascal 

kilowatt 

kilowatt-hour 

liter 

pound 

pound force per foot 

meter 

square meter 

cubic meters 

milligram 

thousandth of an inch 

minute 

megawatt 

-

chromic acid 

x m 

S 14 
oz 

um 

V 

yr 

= ounce 

= micrometer 

= volt 

= year 

(micron) 

XIV 

P.16 

15 
P.17 

TECHNICAL ASSESSMENT OF NEW EMISSION CONTROL TECHNOLOGIES 

USED IN THE HARD CHROMIUM ELECTROPLATING INDUSTRY 

1.0 INTRODUCTION .8 

In 1989, the California Air Resources Board (CARB) approved 

an Airborne Toxic Control Measure (ATCM) for hexavalent chromium 

emissions from chromium plating and anodizing operations. 'Under 

the ACTM for hard chromium electroplating tanks, emission 

reductions are related to the facility-wide emission level 

considering any preexisting control. Facilities with emissions 

less than or equal to 0.91 kg/yr (2 lb/yr) must reduce emissions 

from each tank by 95 percent or achieve an emission limit of 

0.15 mg/Ah (0.002 gr/Ah). Facilities with emissions of at least 

0.91 kg/yr (2 lb/yr) but less than 4.5 kg/yr (10 lb/yr) must 

reduce emissions from each tank by 99 percent or achieve an 

emission limit of 0.03 mg/Ah (0.005 gr/Ah). Facilities with 

emissions of 4.5 kg/yr (10 lb/yr) or greater must reduce 

emissions from each tank by 99.8 percent or achieve an emission 

limit of 0.006 mg/Ah (9.3 x 10"4 gr/Ah). 

The effect of this ATCM was to force development of 

innovative approaches to control that might achieve higher 

reductions than those presently achieved with more conventional 

technologies typically applied in chromium electroplating and 

anodizing operations. Vendors of conventional equipment 

incorporated the use of composite mesh pads into traditional 

control systems in an effort to increase control device 

performance. In addition, based on the high performance levels 

of fiber-bed mist eliminators in controlling sulfuric acid mists, 

these systems were examined to determine their applicability and 

effectiveness in controlling chromic acid emissions. 

Section 2.0 provides background information for the new 

control technologies. Section 3.0 presents brief descriptions of 

each new control technology. Performance data for each 

technology are presented in Section 4.0. Section 5.0 contains 

assessments of cost and environmental impacts associated with 

each technology. Finally, conclusions regarding the 

16 
P.18 

applicability and effectiveness of the new control technologies 

are presented in Section 6.0. 

2.0 BACKGROUND -

f 

2.1 Mesh-Pad Mist Eliminators 

Mesh-pad mist eliminators designed prior to 1986 had a 

single mesh pad consisting of layers of woven material "with fiber 

diameters of 0.09 cm (36 mils). The units were designed for 

vertical gas flow and did not incorporate an internal spray 

system for cleaning of the pad. Because of the tendency of these 

units to plug, they generally were not recommended for 

controlling chromic acid mist. Subsequent generations of meshpad mist eliminators (designed in 1988 - 1989) incorporated two 

or three mesh pads that consisted of material woven from strands 

of fiber with the same fiber diameter, which varied between 0.05 

and 0.09 cm (20 and 36 mils). These newer units were equipped 

with internal spray systems to clean the pads and were designed 

to accommodate the removal of the pads for additional cleaning. 

Thus, the plugging potential was minimized. In addition, these 

units were designed to accommodate horizontal gas flow, 

permitting better drainage of the system. The second generation 

mesh-pad mist eliminator systems had performance levels that 

approximated those obtained through the use of traditional 

packed-bed scrubbers. 

In the early 1990's, the performance level of mesh-pad mist 

eliminator systems was further enhanced by changing the pad 

configuration to facilitate the capture of particles less than 

5 nm (0.20 mil). The most recent design change involves the use 

of a composite mesh pad. These pads differ from traditional mesh 

pads in that the composite pads are woven with layers of material 

with varying fiber diameters instead of layers of material with 

the same fiber diameter. The layers in the center of the 

composite mesh pad consist of extremely small diameter fibers 

(0.01 to 0.02 cm [4 to 8 mils]). The layers on either side of 

the center are made up of progressively larger diameter fibers 

(0.04 to 0.09 cm [16 to 37 mils]). The primary purpose of this 

17 
P.19 

configuration is to produce a coalescing effect. Small mist 

droplets that impinge on the pad coalesce into larger droplets as 

they travel through the finer mesh layers. The enlarged 

particles can then be easily removed in the back layers of the 

pad or in a subsequent stage in the control system. These pads 

may be used in series with other standard types of pad^s in mist 

eliminators, or in conjunction with packed-bed scrubbers, to 

capture chromic acid mists. 

When composite mesh pads are used in mist eliminators, 

multiple pads (typically two to four) are used in series. The 

design of each pad is determined by the size of the mist droplets 

to be collected. The composite pad is typically the second or 

third stage in this type of control system. Irrigation systems 

and provisions for pad removal to facilitate cleaning have been 

incorporated to achieve better chromium emission control 

efficiencies. 

Traditionally, packed-bed scrubbers used to control chromic 

acid mist were horizontal or vertical countercurrent-flow units 

equipped with one or two packed beds followed by a chevron-blade 

mist eliminator section. The designs of these conventional 

scrubber systems have been upgraded in an effort to increase the 

performance level. Overhead spray systems have been added to 

ensure sufficient wetting of the packed bed and to prevent 

chromium buildup. Finally, the addition of a composite mesh pad 

section behind the packed bed(s) has made it possible to improve 

the overall performance of the scrubber unit and eliminate the 

need for a chevron-blade mist eliminator. 

2.2 Fiber-Bed Mist Eliminators 

Fiber-bed mist eliminators have been used predominantly to 

control acid mists from sulfuric, phosphoric, and nitric acid 

plants. Fiber beds have also been used to capture solid 

particulates and mixtures of liquid mists and soluble solids 

(e.g., sodium chloride, ammonium nitrate).1 The transfer of this 

technology to the control of emissions of chromic acid mist from 

18 
P.20 

chromium electroplating and chromic acid anodizing operations has 

occurred only recently. 

Fiber-bed mist eliminators typically consist of one or more 

fiber beds. Each bed consists of a hollow cylinder formed from 

two concentric screens with the fiber packed into the annular 

space between the two screens. These control systems use" 

inertial impaction and Brownian diffusion to remove contaminants 

from a gas stream. Fiber-bed units are designed for horizontal, 

concurrent gas-liquid flow through the bed. As the gas stream 

flows toward the downstream face of the bed, the acid mist in the 

gas stream impacts on the surface of the fibers and drains down 

the outer face of the bed to the sump while the cleaned gas flows 

up and out the top of the unit. These systems are equipped with 

spray nozzles to reduce the potential for plugging. In a further 

effort to prevent plugging, most vendors recommend a prefiltering system. 

3.0 DESCRIPTIONS OF EMISSIONS CONTROL TECHNOLOGIES 

This section presents basic descriptions and operating 

principles for each of the technologies examined. 

The mist eliminator and packed-bed scrubber systems operate 

with inertial impaction and direct interception as the primary 

control mechanisms. Inertial impaction involves the collision of 

large particles with a stationary surface to which they adhere. 

When the mechanism is direct interception, particles attempt to 

follow the streamline around the collection surface, but because 

of their size and relative velocity, they are intercepted by the 

fluid layer that surrounds the collection surface. Collected 

liquid droplets drain to the bottom of the collection device due 

to gravity. 

Another control mechanism used in fiber-bed mist eliminators 

is Brownian diffusion. Brownian diffusion is the random movement 

of particles due to collisions on a molecular level. This random 

motion places the particles on a collision path with the 

collection media. Brownian diffusion is not a major factor for 

particles larger than 3 /xm (0.12 mil). 

I 19 
P.21 

3.1 Composite Mesh-Pad Mist Eliminator Systems 

The principal control mechanisms for mesh-pad mist 

eliminators are droplet impaction and' interception. Inertial 

impaction occurs when larger particles, traveling with sufficient 

velocity, collide with the pad filaments and adhere to their 

surface. Other particles, because of their size and relative 

velocity, are intercepted by the fluid layer surrounding the 

surface of the filament. 

In the composite mesh-pad 'system, the material layers in the 

center of the pad are composed of extremely small-diameter 

(0.01 to 0.02 cm [4 to 8 mil]) fibers. The material layers on 

either side of the center are composed of progressively larger 

(0.04 to 0.09 cm [16 to 37 mil]) diameter fibers. As the gas 

stream flows through the composite mesh pad, the small particles 

that escape the collection device upstream of the mesh pad (e.g., 

packed-bed scrubber or other mesh pads) impinge on the composite 

pad and coalesce into larger droplets. This process is 

accomplished by using a pad comprised of layers of material with 

various fiber diameters and operating the pad at its flood 

point. The flood point is the condition in which the liquid 

flow in the pad is hampered causing liquid to build up in the 

pad. The enlarged particles are then removed in the back side of 

the composite mesh pad or in the backup mesh pad downstream of 

the composite pad. When composite mesh pads are used in series, 

the pressure drop across the system typically ranges from 1.2 to 

1.7 kPa (5 to 7 in. w.c) . 

The performance of mesh-pad mist eliminators is dependent 

upon the fiber diameter, void fraction (amount of free volume), 

and the air velocity passing through the pad. One of the major 

factors that affects mesh-pad mist eliminator performance is the 

tendency of the unit to plug, with the tendency being inversely 

proportional to the size of the fiber. Regular cleaning of the 

pads is critical to optimizing performance. The void fraction 

influences performance because the higher the void fraction, the 

20 
P.22 

greater the resistance to plugging. Mesh pads with higher void 

fractions can handle heavier contaminant loadings. 

Gas stream velocity affects performance because the 

entrained particles must have adequate velocity to collide with 

the fibers. However, gas velocities that are too high can cause 

collected particles to be reentrained in the gas stream. 

Therefore, gas velocities should be maintained high enough to 

optimize collection through inertial impaction yet not cause 

reentrainment. 

Composite mesh pads are used in various configurations and 

are available through many chromium electroplating equipment 

suppliers. 

3.1.1 Composite Mesh Pads Used in Series. 

When mesh pads are used in series, the first stages of the 

unit generally serve to reduce the loading on the pads. The 

first stage is sometimes a single or double set of chevron 

blades. These parallel, chevron-shaped baffles are used to 

remove the large particles, which constitute the majority of 

chromium emissions. The use of chevron blades reduces the 

tendency for the pads to plug. The chevron-blade section may be 

followed by a coarse mesh pad that is used to further reduce the 

loading on the composite pad. This first mesh pad is sometimes 

irrigated with water to promote the coalescing (enlargement) of 

the mist droplets, which makes the droplets easier to remove.2 

The primary purpose of the second pad (composite pad) is to 

increase the size of the particles that penetrated the first pad. 

The larger particles are then collected or reentrained in the 

back side of the second pad.2 The last pad is used to capture 

the reentrained material that was not collected by the previous 

pads. In some mesh-pad systems, all the pads are operated dry 

with periodic washing to clean the pads. 

3.1.2 Composite Mesh Pads Used in Conjunction with Packed-Bed 

Scrubbers. 

Removal of chromic acid mist is accomplished by impingement 

of the droplets on the packing material in the upgraded scrubber 

S 21 
P.23 

systems. The velocity of the gas stream is reduced at the 

scrubber inlet to maximize impingement efficiency. Water is 

sprayed countercurrent to the flow of/8 the gas stream, .thereby 

enlarging the mist droplets contained in the gas stream and 

causing some droplets to drop to the bottom of the scrubber. The 

gas stream'then passes through the packed bed where chromic acid 

droplets impinge on the packing material and are washed to the 

bottom of the scrubber. The packing material used in the newer 

scrubbers has a high surface area-to-volume ratio (presenting 

more impaction opportunities) and the capacity to distribute, 

collect, and re'disperse the scrubbing liquid quickly. Composite 

mesh pads, which are located behind the packed bed, are used to 

remove any reentrained droplets that are carried over from the 

packed-bed section, as well as particles that are too small to be 

captured by the packed bed. One or two coarse mesh pads follow 

the composite pad and are used to remove any enlarged droplets 

that are reentrained from the composite pad. 

3.2 Fiber-Bed Mist Eliminators 

Fiber-bed mist eliminators remove contaminants from a gas 

stream using the mechanisms of inertial impaction and Brownian 

diffusion. When inertial impaction is the principal control 

mechanism, fiber-bed mist eliminators are more efficient than 

other control devices using this mechanism (e.g., typical meshpad mist eliminators and packed-bed scrubbers) because of the 

higher surface area-to-volume ratios. These higher ratios result 

in greater obstruction of the gas flow, permitting additional 

opportunities for impaction of the mist droplets onto the bed 

fibers. Fiber beds designed for contaminant removal by Brownian 

diffusion as well as inertial impaction are the most efficient 

mist eliminators currently available. 

Fiber-bed units are designed for horizontal, concurrent gasliquid flow through the bed. The contaminated gas stream flows 

toward the downstream face of the bed. The acid mist in the gas 

stream impacts on the surface of the fibers and drains down the 

outer face of the bed to the sump while the cleaned gas flows up 

22 
and out the top of the unit. Fiber-bed units are equipped with a 

water spray system to wash down any large particulates that may 

clog the unit. The spray is activated in response to an increase 

in pressure drop over that specified in the design of the unit. 

Pressure drops for impaction units range from 0.15 to 2.0 kPa 

(0.5 to 8 in. w.c) , and pressure drops for Brownian diffusion 

units range from 1.2 to 3.7 kPa (5 to 15 in. w.c) . 

The major factors affecting the performance of fiber-bed 

mist eliminators are the velocity of the inlet gas stream, 

pressure drop across the fiber bed, and the water recirculation 

rate. With impaction-type units, the velocity of the gas flowing 

to the unit must be maintained above a certain lower limit 

because of the decrease in efficiency of inertial impaction at 

low flow rates.3 This lower limit varies, depending on the 

specific design of the impaction bed, but typically ranges from 

30 m/min (100 ft/min) for some fiber beds to 110 m/min 

(350 ft/min) for other beds.4 The Brownian-diffusion type units 

have no lower limit on gas flow rate because mist collection 

increases as the gas flow rate approaches zero. The maximum gas 

flow rate in fiber-bed mist eliminators is defined by the point 

at which: (1) collection efficiency begins to drop below 

acceptable levels, or (2) the gas-phase pressure drop becomes 

excessive.3 Performance may be affected as a result of plugging 

of the bed if the water spray system is not activated in response 

to an increase in the pressure drop. 

Most vendors do not recommend fiber-bed mist eliminators as 

the first stage of the control system because of their tendency 

to plug. It is recommended that coarse pre-filtering be provided 

upstream of the fiber beds to prevent plugging. The prefiltering devices range from a series of mesh pads to a complete 

packed-bed scrubber unit. 

4.0 EMISSIONS TEST DATA 

This section presents the results of full-scale emission 

testing conducted on commercial units used to control chromium 

emissions from hard chromium electroplating and chromic acid 

8 

a 23 
P.25 

anodizing operations. Samples to be analyzed for hexavalent and 

total chromium were obtained through isokinetic sampling using a 

modified EPA Method 5 sampling train 8(40 CFR Part 60 -

Appendix A). The train was modified by eliminating the filter, 

using glass-lined probes and glass nozzles, and using 0.1 normal 

sodium hydroxide instead of water in the impingers. Method 5, 

which also requires the use of EPA Methods 1 through 4, provides 

detailed procedures, equipment criteria, and other considerations 

necessary to obtain accurate and representative emissions 

samples. The collected samples were analyzed using ion 

chromatography with a post-column reactor for hexavalent chromium 

and atomic absorption for total chromium. 

In two of the emissions tests described in this section, 

both hexavalent and total chromium were measured. In the 

remaining two, only total chromium was measured. Results of the 

emissions tests performed by EPA to evaluate performances of 

control techniques for chromium emissions indicate that 

hexavalent chromium constitutes the majority of total chromium 

emissions from chromium electroplating and anodizing operations.5 

Thus, for those tests in which only total chromium was measured, 

the results are assumed to be representative of hexavalent 

chromium levels. 

More detailed information about each test is presented in 

tabular form in Appendix A. 

4.1 Composite Mesh-Pad Tests 

4.1.1 Mesh-Pad Mist Eliminator--Precision Engineering. Seattle. 

Washington6 

Emission source tests were conducted by EPA at Precision 

Engineering on December 17-19, 1991, to evaluate the performance 

of a state-of-the-art mesh-pad mist eliminator. Precision 

Engineering is a medium size job shop that performs hard chromium 

plating of industrial rolls, hydraulic cylinders, and 

miscellaneous small parts. 

4.1.1.1 Process Description. The plating shop typically 

operates 24 hours per day, 5 days per week. There are six hard 

9 

8 24 
P.26 

chromium plating tanks at this facility. During the source 

tests, Tanks 1, 2, and 7 were tested. Table l presents the 

dimensions and operating parameters^for each process tank. All 

three plating tanks are divided into two cells and each cell is 

equipped with a rectifier to control the current flow. Current 

ratings (per cell) of the rectifiers are 5,000 A, 3,000 A,- and 

10,000 A for Tanks 1, 2, and 7, respectively. The plating 

solution in each tank consists of chromic acid at a concentration 

of 250 g/L (33 oz/gal). The temperature of the plating solution 

is maintained at approximately 60 C (140°F). 

TABLE 1. DIMENSIONS AND OPERATING PARAMETERS FOR THE HARD 

CHROMIUM PLATING TANKS AT PRECISION ENGINEERING, 

SEATTLE, WASHINGTON 

Tank 

NO. 

Dimensions 

(1, w, d) , 

m (ft) 

2.0, 1.3, 3.7 

(6.5, 4.2, 12.0) 

2.0, 1.3, 3.7 

(6.5, 4.2, 12.0) 

1.2, 1.8, 5.5 

(4.0, 5.9, 18.0) 

Capacity, 

L (gal) 

9,280 

(2,450) 

9,280 

(2,450) 

11,830 

(3,120) 

Maximum rated 

current per 

cell, A 

5,000 

3,000 

10,000 

1 

2 

7 

All of the plating tanks are serviced by overhead hoists 

that are used to transfer parts in and out of the tanks. Heating 

and cooling systems are located in each tank to maintain uniform 

solution temperature. In addition, each of the tanks is equipped 

with an air agitation system to aid in maintaining uniform bath 

concentration and temperature. 

4.1.1.2 Air Pollution Control.2*

6 

A schematic of the ventilation system and control device 

servicing the plating tanks is shown in Figure 1. The system was 

installed in 1991. Each tank is equipped with a double-sided 

hood for ventilation. Moisture extractors are located in the 

10 

S 25 
P.27 

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t/i 00 00 OO 00 oo oo 

IIIIII I 

0000000 

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0) 

c 

•H 

tj. 

c 

w 

c 

0 

-H 

w 

•H 

o 

(1). 

J-1 

cu 

(0 

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tA 

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W 

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o 

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T3 

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ra 

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11 

26 
P.28 

hood uptakes to remove the coarser mist droplets from the exhaust 

stream, thereby reducing the inlet loading to the mist 

eliminator. Tanks l and 2 are ducted?'together to form one inlet 

leg to the mist eliminator, while Tank 7 is ducted separately to 

form another inlet leg to the mist eliminator. The two inlet 

legs join just prior to the inlet plenum of the mist eliminator. 

The mesh-pad mist eliminator is located on the roof of the 

plating shop and is a first generation Spectra V manufactured by 

KCH Services, Inc. The unit consists of a set of chevron-blade 

baffles followed by a series of three mesh pads. The mesh pads 

were manufactured by Kimre, Inc The first pad in the series is 

a coarse mesh that consists of material woven from strands of 

fiber with the same fiber diameter, which ranges from 0.04 to 

0.09 cm (16 to 37 mils). This pad removes the majority of the 

chromic acid mist particles. The second pad (the composite mesh 

pad) serves to enlarge the size of the particles that penetrate 

the first pad, and these particles then impinge on the back side 

of the second pad and coalesce into larger droplets. This pad is 

comprised of layers of material with fiber diameters typically 

ranging from 0.005 to 0.04 cm (2 to 16 mils). The material 

layers in the center of this second pad contain the smallest 

diameter fibers, with the layers on either side of the 

center containing progressively larger diameter fibers. The 

purpose of the third pad, which is identical to the first pad, is 

to remove any reentrained droplets carried over from the second 

pad. 

The design pressure drop across the mist eliminator is 

1.7 kPa (7 in. w.c) . An increase in pressure drop above the 

normal operating range for a given pad indicates that the pad 

*Mention of trade names or commercial products is not 

intended to constitute endorsement or recommendation for 

use. 

12 

S 27 
P.29 

needs to be washed down to remove chromium that has built up on 

the pad. This is accomplished with a series of spray nozzles 

located in front of each mesh pad. 

4.1.1.3 Process Conditions During Testing.6 Three sample ' 

runs were conducted at each of the two inlet locations (A and B) 

and at the outlet (stack, C) of the mist eliminator. Testing at 

the three locations was performed simultaneously. Each test run 

was 4 to 6 hours in duration. Process operating parameters 

monitored during each sample run included the voltage, current, 

ampere-hours, and-plating solution temperature for each plating 

tank in operation. Average values for each sample run are 

presented in Table 2. Hydraulic cylinders were plated during 

each test run. The surface areas of the parts plated during the 

test program are included in Table 2. Pressure drops across each 

mesh pad and across the overall unit were monitored during each 

test run and no increase in pressure drop was noted. 

4.1.1.4 Results of Emissions Testing.6 Results of the 

emissions testing are presented in Tables 3a and 3b. Total 

chromium emissions from Tanks 1 and 2 measured at Inlet A 

averaged 0.35 mg/dscm (0.15 x 10"3 gr/dscf), or 5.6 x 10"3 kg/hr 

(12 x 10"3 lb/hr). At Inlet B, total chromium emissions from 

Tank 7 averaged 0.15 mg/dscm (0.06 x IO"3 gr/dscf), or 

1.3 x IO"3 kg/hr (2.9 x IO"3 lb/hr). Total chromium emissions 

measured at the outlet of the mesh-pad mist eliminator averaged 

0.011 mg/dscm (5 x IO"6 gr/dscf), or 0.27 x IO"3 kg/hr 

(0.58 x IO"3 lb/hr). 

Hexavalent chromium emissions from Tanks 1 and 2 measured at 

Inlet A averaged 0.34 mg/dscm (0.15 x IO"3 gr/dscf), or 

5.3 x IO'3 kg/hr (12 x IO"3 lb/hr). Hexavalent chromium 

emissions from Tank 7 at Inlet B averaged 0.15 mg/dscm 

(0.06 x IO"3 gr/dscf), or 1.3 x IO"3 kg/hr (2.9 x IO"3 lb/hr). 

At the outlet of the mesh-pad mist eliminator, hexavalent 

chromium emissions averaged 0.010 mg/dscm (0.005 x IO"3 gr/dscf), 

or 0.25 x IO"3 kg/hr (0.55 x IO"3 lb/hr). 

13 

m a 28 
P.30 

TABLE 2. AVERAGE OPERATING PARAMETERS DURING EACH EMISSIONS 

TEST RUN AT PRECISION ENGINEERING, SEATTLE, WASHINGTON 

Run 

No. 

1 

2 

3 

-

Tank 

No. 

IA 

IB 

2A 

2B 

7A 

7B 

IA 

IB 

2A 

2B 

7A 

7B 

IA 

IB 

2A 

2B 

7A 

7B 

Operating 

voltage, 

V 

7.0 

7.0 

7.6 

7.6 

8.0 

6.4 

6.3 

7.2 

7.4 

6.6 

6.4 

6.4 

6.4 

7.7 

7.8 

6.0 

7.3 

Operating 

current, 

A 

4,300 

3,700 

2,300 

1,400 

7,000 

3,600 

3,400 

1,700 

1,850 

1,300 

2,000 

2,970 

2,800 

2,000 

1,700 

1,000 

7,200 

Temperature 

of plating 

solution, 

°C (°F) 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 

140 « 

Surface 

area 

plated 

m

2 

368 

167 

332 

368 

167 

469 

260 

167 

474 

-(ftz) 

(3,960) 

(1,800) 

(3,570) 

(3,960) 

(1,800) 

(5,050) 

(2,800) 

(1,800) 

(5,100) 

14 

a 29 
TABLE 3a. PERFORMANCE DATA FOR THE MESH-PAD MIST ELIMINATOR AT PRECISION 

ENGINEERING, SEATTLE, WASHINGTON (TOTAL CHROMIUM TEST RESULTS) 

Inlet A Inlet B Outlet (C) 

Total chromium emissions Total chromium emissions Total chromium emissions 

Run Process kg/hr Process kg/hr Process kg/hr % EffiNo. current, Ah mg/dscm (IO"3

) mg/Ah current, Ah mg/dscm (IO*3) mg/Ah current, Ah mg/dscm (IO'3) mg/Ah ciencya 

1 

2 

3 

AVG 

67,000 

42,000 

38,000 

49,000 

0.31 

0.29 

0.45 

0.35 

4.8 

4.4 

7.5 

5.6 

0.429 

0.419 

0.789 

0.546 

42,000 

28,700 

32,800 

34,500 

0.15 

0.14 

0.15 

0.15 

1.4 

1.3 

1.2 

1.3 

0.200 

0.181 

0.146 

0.176 

109,000 

70,700 

70,700 

83,500 

0.013 

0.011 

0.009 

0.011 

0.32 

0.25 

0.23 

0.27 

0.018 

0.014 

0.013 

0.015 

94.8 

95.6 

97.4 

95.9 

•-Efficiencies are calculated from mass emission rates, and the average is based on averaging efficiencies for each run. Because there were two inlet 

sampling locations, efficiencies were determined by using the sums of the two inlet mass emission rates. 

ui 

CO 

o 

TABLE 3b. PERFORMANCE DATA FOR THE MESH-PAD MIST ELIMINATOR AT PRECISION 

ENGINEERING, SEATTLE, WASHINGTON (HEXAVALENT CHROMIUM TEST RESULTS) 

Run 

No. 

1 

2 

3 

AVG 

Process 

current, Ah 

67,000 

42,000 

38,000 

49,000 

Inlet A 

Hexavalent chromium 

emissions 

mg/dscm 

0.29 

0.28 

0.44 

0.34 

kg/hr 

(IO"3) 

4.6 

4.2 

7.2 

5.3 

mg/Ah 

0.411 

0.400 

0.758 

0.523 

Process 

current, Ah 

42,000 

28,700 

32,800 

34,500 

Inlet B 

Hexavalent chromium 

emissions 

mg/dscm 

0.15 

0.13 

0.17 

0.15 

kg/hr 

(IO"3) 

1.4 

1.1 

1.4 

1.3 

mg/Ah 

0.200 

0.153 

0.171 

0.175 

Process 

current, Ah 

109,000 

70,700 

70,700 

83,500 

Outlet (C) 

Hexavalent chromium 

emissions 

kg/hr 

mg/dscm (\0 ) 

0.014 0.34 

0.009 0.22 

0.008 , 0.20 

0.010 0.25 

mg/Ah 

0.019 

0.012 

0.011 

0.014 

% Efficiency* 

94.3 

95.8 

97.7 

95.9 

Efficiencies are calculated from mass emission rates, and the average is based on averaging efficiencies for each run. Because there were two inlet 

sampling locations, efficiencies were determined by using the sums of the two inlet mass emission rates. 
P.32 

In calculating the overall removal efficiency of the meshpad mist eliminator, the total mass emission rates for Inlets A 

and B were compared to the outlet mass emission rate. The 

apparent effectiveness of the moisture extractors is indicated by 

the inlet loading values, which, despite the relatively high 

process current, are unusually low. The removal efficiency 

averaged 95.9 percent for both total chromium and hexavalent 

chromium. The average total current applied to the tanks during 

outlet testing was 83,500 Ah. 'Therefore, the process emission 

rates based on total and hexavalent chromium measurements were 

0.015 mg/Ah (2^3 x IO"4 gr/Ah) and 0.014 mg/Ah (2.2 x IO"4 

gr/Ah). 

4.1.2 Mesh-Pad Mist Eliminator--Monroe Auto Equipment. Hartwell. 

Georgia7 

Source testing was conducted at Monroe Auto Equipment, 

Hartwell, Georgia, on December 18 - 20, 1991, to evaluate the 

performance of a composite mesh-pad mist eliminator. Emissions 

testing was performed by IEA, Inc, of Research Triangle Park, 

North Carolina, and observed by a representative of the U.S. EPA. 

The Monroe Auto Equipment plating operation uses a chemical fume 

suppressant to inhibit misting. Therefore, testing was performed 

with and without the fume suppressant in the plating bath. 

Monroe Auto Equipment performs hard chromium electroplating 

of shock absorbers of various sizes. The plating line is 

typically operated 5 days per week and 16 hours per day. 

4.1.2.1 Process Description.7*

8 The shock absorber rods 

are loaded into a carrier, six at a time, and the carrier is 

conveyed from tank to tank through the plating line. There is 

one chromium electroplating tank in the plating line; it is 1.4 m 

(4.5 ft) wide by 9.1 m (30 ft) long by 0.91 m (3.0 ft) deep and 

holds about 11,400 L (3,000 gal) of plating solution. The 

plating solution in the tank contains chromic acid in a 

concentration of 240 g/L (32 oz/gal). The normal operating bath 

temperature is 54°C (130°F). The plating tank is equipped with 

heating and cooling systems and is air agitated to maintain a 

16 

a 3i 
P.33 

uniform plating bath temperature and composition. The tank is 

serviced by an 11,000 A, 12 V rectifier and is operated at a 

current ranging from 3,300 A to 10,00:0 A depending on the length 

of the shock absorber rods. 

4.1.2.2 Air Pollution Control.2,7,9 The chromium emissions 

from the plating tank are exhausted to a mesh-pad mist eliminator 

system consisting of two sets of double-sided chevron blades 

followed by a series of three mesh pads. The mesh pads were 

manufactured by Kimre, Inc. The control system, a Spectra V, 

manufactured by KCH Services, Inc , was installed in November of 

1991. 

The first pad in the series of pads is a coarse mesh that 

typically consists of material woven from strands of fiber with 

the same fiber diameter, which varies between 0.04 and 0.09 cm 

(16 and 37 mils). This pad removes the majority of the chromic 

acid mist particles. The second pad (the composite mesh pad) 

serves to enlarge the size of the particles that penetrate the 

first pad, and these larger particles then impinge on the back 

side of the second pad. This pad is comprised of layers of 

material with fiber diameters typically ranging from 0.005 to 

0.04 cm (2 to 16 mils). The material layers in the center of 

this second pad contain the smallest diameter fibers, with the 

layers on either side of the center containing progressively 

larger diameter fibers. The purpose of the third pad, which is 

identical to the first pad, is to remove any reentrained droplets 

carried over from the second pad. 

The mesh-pad mist eliminator system is designed to 

accommodate a flow rate of 800 m3/min (28,000 ft3/min) and has a 

design pressure drop across the entire system of 1.3 kPa (5.25 

in. w.c) . The control system is operated dry but is equipped 

Mention of trade names or commercial products is not 

intended to constitute endorsement or recommendation for 

use. 

17 

S 32 
P.34 

with a spray system to wash the individual pads when the pressure 

drop across the system increases. 

During the emissions testing, a ^chemical fume suppressant 

(an M& T Fumetrol 210 combination foam blanket and wetting 

agent ) was used during half of the emissions test runs. The 

"foam is designed to inhibit chromic acid misting from the plating 

bath by trapping the mist in the foam layer. The wetting agent 

inhibits misting by lowering the surface tension of the plating 

bath, allowing the gases to escape at the surface with less of a 

bursting effect. 

4.1.2.3 Process Conditions During Testing.7 Six emissions 

test runs were conducted at the inlet and outlet of the mesh-pad 

mist eliminator system to characterize the overall performance. 

Each test run was approximately two hours in duration. Test Runs 

1, 3, and 4 were performed when no fume suppressant was used, and 

test Runs 2, 5, and 6 were performed when the combination foam 

blanket and wetting agent was used in the bath. Table 4 presents 

the average operating parameters (voltage, current, and 

temperature of the plating solution) monitored during each test 

run. 

The pressure drop across the mesh-pad mist eliminator system 

did not increase during any of the test runs; therefore, no 

washing of the pads was necessary. The foam blanket used during 

test Runs 2, 5, and 6 was maintained at a thickness between 3 and 

8 cm (1 and 3 in.) with the heavier layers in the corners of the 

tank. 

4.1.2.4 Results of Emissions Testing.7 Table 5 presents 

the performance data for the mesh-pad mist eliminator system 

tested at Monroe Auto Equipment. Emissions measured at the inlet 

*Mention of trade names or commercial products is not 

intended to constitute endorsement or recommendation for 

use. 

18 

fi 3 3 
P.35 

TABLE 4. AVERAGE OPERATING PARAMETERS MONITORED DURING 

EACH EMISSIONS TEST RUN AT MONROE AUTO EQUIPMENT, 

HARTWELL, GEORGIA 

Run 

No. 

1 

2 

3 

4 

5 

6 

Operating 

voltage, 

V 

6.4 

6.4 

6.4 

. 6.3 

7.2 

7.2 

Operating 

current, 

A 

6,800 

6,800 

6,800 

6,800 

10,100 

10,200 

Temperature 

of plating 

solution, 

°C (°F) -

141 

141 

141 

140 

144 

143 

when a fume suppressant was not used on the plating bath averaged 

0.95 mg/dscm (4.2 x IO"4 gr/dscf), or 41.6 x IO"3 kg/hr 

(91/7 x IO"3 lb/hr). Emissions measured at the outlet of the 

mesh-pad mist eliminator system when a fume suppressant was not 

used averaged 0.011 mg/dscm (0.5 x IO"5 gr/dscf), or 

0.52 x 10"3 kg/hr (1.1 x 10"3 lb/hr). The removal efficiency of 

the mesh-pad mist eliminator control system in the absence of a 

fume suppressant averaged 98.7 percent. The average total 

current applied to the electroplating tank during outlet testing 

averaged 13,600 Ah. Therefore, the process emission rate, based 

on total chromium measurements, was 0.079 mg/Ah (1 x 10"3 gr/Ah). 

When a fume suppressant was used, emissions measured at the 

inlet to the mesh-pad mist eliminator system ranged from 

0.17 mg/dscm to 0.60 mg/dscm (8 x IO"5 to 26 x IO"5 gr/dscf), or 

7.35 x IO"3 to 26.3 x IO"3 kg/hr (16.2 x IO"3 to 60.0 x IO"3 

lb/hr). Emissions measured at the inlet when the foam blanket 

was used averaged 0.38 mg/dscm (16 x IO"5 gr/dscf), or 16.7 x 

10"3 kg/hr (36.9 x IO"3 lb/hr). 

The average of emissions measured at the outlet of the 

control device when the fume suppressant was used was 

19 

8 34 
TABLE 5. PERFORMANCE DATA FOR THE MESH-PAD MIST ELIMINATOR AT 

MONROE AUTO EQUIPMENT, HARTWELL, GEORGIA 

o 

Run 

No. 

Process 

Inlet 

Total chromium emissions 

current, Ah mg/dscm 

Without Fume Suppressant 

1 

3 

4 

AVG 

13,600 

13,600 

13,600 

13,600 

With Fume Suppressant 

2 

5 

6 

AVG 

13,600 

20,200 

20,400 

18,100 

0.97 

1.06 

0.82 

0.95 

0.17 

0.60 

0.36 

0.38 

kg/hr 

(10"3) 

41.7 

47.1 

35.9 

41.6 

7.35 

26.3 

16.6 

16.7 

mg/Ah 

6.14 

6.94 

5.28 

6.12 

1.08 

2.60 

1.63 

1.77 

Process 

current, Ah 

13,600 

13,600 

13,600 

13,600 

13,600 

20,200 

20,400 

18,100 

Outlet 

Total chromium emissions 

mg/dscm 

0.009 

0.012 

0.013 

0.011 

0.005 

0.007 

0.012 

0.008 

kg/hr 

(IO"3) 

0.39 

0.56 

0.61 

0.52 

0.23 

0.31 

0.54 

0.36 

mg/Ah 

0.063 

0.083 

0.090 

0.079 

0.035 

0.033 

0.056 

0.041 

% Efficiency8 

99.1 

98.8 

98.3 

98.7 

96.9 

,/98.8 

96.7 

97.5 

"Efficiencies are calculated from mass emission rates (kg/hr), and the average is based on averaging efficiencies for each run. 
P.37 

0.008 mg/dscm (0.3 x IO"5 gr/dscf), or 0.36 x IO"3 kg/hr 

(0.79 x IO"3 lb/hr). The removal efficiency of the mesh-pad mist 

eliminator system when a fume suppressant was used averaged 

97.5 percent. The average total current applied to the tank 

during outlet testing was 18,100 Ah. Therefore, the process 

emission rate, based on total chromium measurements, was 

0.041 mg/Ah (1 x IO"3 gr/Ah). 

The data presented in Table 5 indicate a lower emission rate 

at the inlet when the combination foam blanket and wetting agent 

was present in the plating tank. These decreased inlet 

concentrations may have resulted in slightly lower mesh-pad mist 

eliminator chromium removal efficiencies for the runs associated 

with the use of the fume suppressant. However, the performance 

of the overall system remained the same, as indicated by the 

outlet concentration levels for all six runs. This suggests that 

use of the fume suppressant represents a redundant level of 

control. 

4.1.3 Packed-Bed Scrubber/Mesh-Pad Mist Eliminator System--Remco 

Hydraulics. Inc., Willits, California10 

In February 1989, Remco Hydraulics, Inc. installed a control 

system consisting of a packed-bed scrubber with a chevron-blade 

section to control emissions from their chromium electroplating 

operations. Emission tests showed that this control system could 

not achieve California's proposed hexavalent chromium standard of 

0.006 mg/Ah. The system was then modified by eliminating the 

chevron-blade section and installing a two-stage mesh-pad mist 

eliminator. The modified system was tested in August 1989 but 

again failed to meet the proposed standard. It was suspected 

that bypass problems due to seal degradation were probably 

contributing to the inadequate performance levels. Both mesh 

pads were replaced with new pads, which were installed in a 

housing with a double seal system to eliminate the bypass 

problems. A series of spray nozzles was added to the unit for 

continuous pad irrigation. Emissions testing was conducted 

21 

a 36 
P.38 

June, 1991, and the control system met the required emission 

level. 

The U.S. EPA directed the source/testing of the packed-bed 

scrubber/mesh-pad mist eliminator system at Remco Hydraulics, 

Inc., Willits, California on June 19-21, 1991. The performance 

of the emission control system, which incorporates the-use~of a 

composite mesh pad, was determined by testing at the inlet and 

outlet of the system. 

Remco is a large job shop that performs hard chromium 

electroplating of hydraulic cylinders, shock absorbers, offshore 

equipment, and accumulators. The shop typically operates 5 days 

per week, 16 hours per day, and 52 weeks per year. 

4.1.3.1 Process Description.10 There are seven hard 

chromium electroplating tanks at this facility. Table 6 presents 

the descriptions and maximum operating parameters for each of 

these tanks. The plating solution in each tank consists of 

chromic acid at a concentration of 240 g/L (32 oz/gal), and 

sulfuric acid, a catalyst, at a concentration of 2.4 g/L 

(0.32 oz/gal). The normal operating bath temperature range is 

49°C to 54°C (120°F to 130°F). All tanks are equipped with 

heating and cooling systems and are air agitated to maintain 

uniform plating bath temperature and composition. Tanks 1 and 2 

are divided into two cells with one rectifier used to control the 

current flow in each cell. Tanks 3 through 5 are each controlled 

by one rectifier, and Tanks 6 and 7 are each controlled by two 

rectifiers. 

4.1.3.2 Air Pollution Control.10 Tanks 1 and 2 are 

equipped with double-sided hoods and the round tanks (Nos. 3 

through 7) are equipped with circular hoods. During the tests, 

the ventilation system appeared to be effective in directing the 

mist from the plating tanks to the control device. The chromium 

emissions from the plating tanks are exhausted to the packed-bed 

scrubber/mesh-pad mist eliminator system located on a mezzanine 

beside the plating tanks. The capture and control system was 

22 

S 37 
P.39 

TABLE 6. DIMENSIONS AND OPERATING PARAMETERS FOR THE SEVEN 

HARD CHROMIUM PLATING TANKS AT REMCO HYDRAULICS, INC., 

WILLITS, CALIFORNIA 

Dimensions, 

(1, w, d) or 

Tank (dia, ht) , Capacity, 

No. m (ft) L (gal) 

Maximum 

rated 

voltage 

per cell, 

V 

Maximum rated 

current 

per cell, 

A 

1 

2 

3 

4 

5 

6 

7a 

4 

(13. 

3 

(12. 

.1, 1.5, 2.1 

3, 4.9, 7.0) 

.7, 1.7, 2.1 

0, .5.5, 6.9) 

0.91, 9.4 

(3.0, 31.0) 

1.2, 11.6 

(4.0, 38.0) 

0.91, 6.1 

(3.0, 20.0) 

1.2, 15.2 

(4.0, 50.0) 

1.2, 18.3 

(4.0, 60.0) 

11,360 

(3,000) 

11,360 

(3,000) 

6,060 

(1,600) 

13,250 

(3,500) 

4,000 

(1,060) 

17,790 

(4,700) 

21,580 

(5,700) 

2 

2 

2 

2 

@ 

@ 

@ 

@ 

15 

15 

15 

15 

15 

15 

15 

10 

12 

,000; 3,000 

,000; 3,000 

8,000 

16,000 

8,000 

2 @ 12,000 

2 @ 12,000 

-Plating tank was not operated during the emission test, 

23 

I 38 
P.40 

manufactured by Duall Industries, Inc. The mesh pads were 

manufactured by Kimre, Inc. 

Packing depth in more conventional scrubbers is about 0.30 m 

(1.0 ft). The scrubber at this facility has a packed-bed 1.8 m 

(6.0 ft) deep, followed by the mesh-pad mist eliminator section 

located directly behind the scrubber. Because of the extended 

depth of the packed-bed, the scrubber is also equipped with an 

overhead spray system in which spray nozzles are used to ensure 

sufficient wetting of the bed packing media. The unusually deep 

packed bed was installed to meet the State of California's 

proposed regulation governing hexavalent chromium emissions. 

Figure 2 presents a detailed schematic of the control 

system. The plating tanks are ventilated by a 50-hp fan located 

downstream of the scrubber. The design airflow rate of the 

scrubber is 850 m3/min (30,000 ft3/min). The scrubbing water 

flow rate is approximately 1,140 L/min (300 gal/min). The design 

pressure drop across the entire control system (packed-bed 

scrubber and mesh-pad mist eliminator) is 1.5 kPa (6.0 in. w.c) . 

Within the scrubber system, the velocity of the gas stream 

is reduced to less than 150 m/min (500 ft/min), and the gas 

stream is humidified by a stream of water, which is sprayed 

countercurrent to the gas flow through 22 spray nozzles. The 

saturated gas stream then passes through a packed bed consisting 

of spherical polypropylene packing. The bed is approximately 

2.4 m (8.0 ft) high, 3.0 m (10 ft) wide, and 1.8 m (6.0 ft) deep. 

The design pressure drop across the bed packing media is 0.30 kPa 

(1.2 in. w.c) . Entrained mist and water droplets impinge on the 

packing and drain to the recirculation tank. A series of 5 water 

lines with 10 spray nozzles per line are located over the packed 

Mention of trade names or commercial products is not 

intended to constitute endorsement or recommendation for 

use. 

2 4 

a 39 
to 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

SAMPLING 

LOCATION A AT INLET 

LOCATION B_ AT INLET 

LOCATION C_ AT OUTLET 

LOCATION D_ TANK 1 

LOCATION E_ TANK 2 

LOCATION £ TANK 3 

LOCATION G_ TANK 4 

LOCATION H^ TANK 5 

LOCATION J_ TANK 6 

LOCATION J^ TANK 7 

LOCATION K SCRUBBER WATER 

Figure 2. Schematic of control system at Remco Hydraulics, Inc., Willits, California, 

O 

j*> 
P.42 

bed. The spray system is used for complete wetting of the 

packing to prevent chromium buildup and to aid in chromium 

removal. "' 

Behind the packed bed, a mist elimination section removes 

entrained water droplets. The first stage of this section allows 

large droplets to settle by gravity to the bottom of the 

scrubber. The next stage consists of a composite mesh pad 

followed by a backup mesh pad. In the composite mesh pad, the 

fibers in the center of the pad are 0.01 to 0.02 cm (4 to 8 mils) 

in diameter. The diameters of the fibers in the layers on either 

side of the center range from 0.04 to 0.09 cm (16 to 37 mils). 

Small particles that escaped the packed bed coalesce into large 

droplets as they pass through the inner layers of the pad. The 

enlarged particles are then removed in the back section of the 

composite pad or in the backup mesh pad. The backup mesh pad has 

multiple layers of material with fibers 0.9 cm (37 mils) in 

diameter. Each of the mesh pads is split into two sections, each 

approximately 2.4 m (8 ft) high and 0.09 m (3.7 ft) wide. The 

composite mesh pad is 16.5 cm (6.5 in.) thick, and the backup pad 

is 6.1 cm (2.4 in.) thick. The design pressure drop across the 

mesh pads is 1.2 kPa (4.75 in. w.c) . The design of the mesh-pad 

section specified continuous irrigation of the composite mesh 

pad. The backup pad is designed to be-washed down on an asneeded basis. 

4.1.3.3 Process Conditions During Testing.10 Three mass 

emission test runs were conducted simultaneously at the inlet and 

outlet of the packed-bed scrubber/mesh-pad mist eliminator system 

to characterize the overall performance of the control system. 

Six of the seven chromium electroplating tanks ducted to the 

control system were in operation, and the process was operating 

normally during the tests. Table 7 presents the average 

operating parameters monitored during each emissions test run. 

Prior to testing, the exhaust rate through the scrubber was 

determined to be less than half of the design air flow rate. 

Modifications made to increase the exhaust rate included 

26 

I 41 
P.43 

TABLE 7. AVERAGE OPERATING 

EMISSIONS TEST RUN AT REMCO 

PARAMETERS MONITORED DURING EACH 

HYDRAULICS, INC., WILLITS, CALIFORNIA 

Run 

No. 

Tank 

No. 

Surface area 

plated, 

nr (ft-4) 

Operating 

voltage, 

V 

Operating 

current, 

A 

Temperature 

of plating 

solution, 

°C (<>F) 

1 

2 

3 

1-A 

1-B 

2-A 

2-B 

3 

4 

5 

6 

1-A 

1-B 

2-A 

2-B 

3 

4 

5 

6 

1-A 

1-B 

2-A 

2-B 

3 

4 

5 

6 

1.4 

0.95 

1.9 

1.1 

3.3 

3.3 

3.3 

4.8 

1.4 

0.95 

1.9 

1.1 

3.3 

3.3 

3.3 

4.8 

1.4 

0.95 

1.9 

1.1 

3.3 

3.3 

3.3 

4.8 

(15) 

(10) 

(20) 

(12) 

(36) 

r36) 

(36) 

51) 

15) 

(10) 

20) 

12) 

36) 

36) 

36) 

51) • 

15) 

(10) 

20) 

12) 

36) 

36) 

36) 

51) 

8.0 

8.3 

9.0 

8.0 

7.7 

12.1 

7.1 

11.9 

11.8 

8.0 

8.4 

9.6 

8.0 

7.4 

11.4 

7.0 

11.5 

11.5 

8.0 

8.4 

9.6 

8.0 

7.7 

11.2 

7.2 

11.4 

11.2 

8,600 

2,700 

8,800 

2,700 

6,300 

10,900 

7,300 

7,400 

5,700 

8,500 

2,700 

9,400 

2,700 

5,800 

10,600 

7,400 

7,100 

5,800 

8,300 

2,700 

9,600 

2,700 

6,000 

10,400 

7,300 

6,700 

5,400 

52 ( 

52 1 

53 1 

53 

51 ( 

59 ( 

56 ( 

57 ( 

57 

52 1 

53 

-52 

52 

52 < 

59 

55 

58 

58 

49 

49 

51 

51 

49 

57 

53 

52 

52 

126) 

126) 

127) 

127) 

124) 

139) 

133) 

134) 

134) 

126) 

127) 

126) 

126) 

125) 

138) 

131) 

137) 

137) 

121) 

121) 

(123) 

(123) 

(121) 

(135) 

(127) 

(125) 

(125) 

27 

e 42 
P.44 

increasing the fan speed and shutting down the recirculation 

sprays to the composite mesh pad. These procedures increased the 

exhaust rate to approximately 84 percent of the design rate, 

allowing the scrubber to operate within its intended gas velocity 

range. The adjustments also resulted in the capture efficiency 

of the ventilation system being sufficient to service all six of 

the operating plating tanks. The shutting down of the 

recirculation sprays to the composite mesh pad lowered the 

pressure drop across the pad to about 50 percent of the design 

value. Nevertheless, the scrubber/mist eliminator system was 

operating at or near optimal conditions during the course of the 

testing. Because the unit was designed to have continuous 

washdown, the vendor was contacted to determine the potential 

effects on the performance of the unit if only periodic washdown 

were used. The vendor advised that periodic washdown would be 

sufficient but recommended that the pressure drop across the unit 

be closely monitored to minimize the plugging potential. The 

pressure drop was monitored throughout the testing period and no 

increase in pressure drop was observed. 

During emissions testing, dummy rods were plated in each of 

the tanks. The total surface area of the parts plated during 

each emission test run is given in Table 7. 

Pressure drops across the packing media and mesh pads were 

monitored during each test run. The average pressure drops 

across the packing media and mesh pads were 0.30 kPa 

(1.2 in. w.c.) and 0.60 kPa (2.3 in. w.c) , respectively. 

4.1.3.4. Results of Emissions Testing.10 Measurements to 

determine emissions concentrations at the inlet to the scrubber 

system were made at two locations. Measurements taken at Inlet A 

represent emissions vented from Tanks 1 and 2, while Inlet B 

readings measured emissions vented from the remaining 4 tanks. 

Performance data for the control system are summarized in 

Tables 8a and 8b. Total chromium emissions measured at inlet A 

of the control device averaged 131 mg/dscm (0.057 gr/dscf), or 

28 

fi 4 3 
TABLE 8a. PERFORMANCE DATA FOR THE PACKED-BED SCRUBBER/MESH-PAD MIST ELIMINATOR 

SYSTEM AT REMCO HYDRAULICS, INC., WILLITS, CALIFORNIA 

(TOTAL CHROMIUM TEST RESULTS) 

Run 

No. 

1 

2 

3 

AVG 

Process 

current, Ah 

136,800 

140,500 

139,100 

138,800 

Inlet A 

Total chromium 

mg/dscm kg/hr mg/Ah 

150 3.16 139 

109 2.30 98.3 

134 2.95 127 

131 2.80 121 

Process 

current, Ah 

229,700 

221,300 

213,700 

225,500 

Inlet B 

Total chromium 

mg/dscm 

1.09 

1.83 

15.6b 

1.46 

kg/hr mg/Ah 

0.018 0.47 

0.030 0.82 

0.268b 7.53b 

0.024 0.65 

Process 

current, Ah 

381,400 

376,200 

366,700 

374,800 

Outlet 

Total chromiurr 

mg/dscm 

.0.006 

0.003 

0.009 

0.006 

kg/hr 

2.55X10"4 

1.38X10-4 

3.52X10"4 

2.48xl0"4 

l 

mg/Ah 

0.004 

0.002 

0.006 

0.004 

% Efficiency11 

99.992 

99.994 

99.993 

"Efficiencies are calculated from mass emission rates (kg/hr), and the average is based on averaging efficiencies for each run. 

"During Run 3 at Inlet B, it was suspected that the probe may have contacted the duct wall. Therefore, the values obtained for Run 3 at Inlet B 

were not used to calculate averages or efficiency. 

to 

vo TABLE 8b. PERFORMANCE DATA FOR THE PACKED-BED SCRUBBER/MESH-PAD MIST ELIMINATOR 

SYSTEM AT REMCO HYDRAULICS, INC., WILLITS, CALIFORNIA 

(HEXAVALENT CHROMIUM TEST RESULTS) 

Run 

No. 

1 

2 

3 

AVG 

Process 

current, Ah 

136,800 

140,500 

139,100 

138,800 

Inlet A 

Hexavalent chrc 

mg/dscm 

156 

118 

145 

140 

mium 

kg/hr mg/Ah 

3.28 

2.50 

3.19 

2.99 

144 

107 

138 

130 

Process 

current, Ah 

229,700 

221,300 

213,700 

225,500 

Inlet B 

Hexavalent chromium 

mg/dscm 

1.20 

1.85 

16.9b 

1.52 

kg/hr mg/Ah 

0.020 0.52 

0.031 0.83 

0.292b 8.20b 

0.025 0.68 

Process 

current, Ah 

381,400 

376,200 

366,700 

374,800 

Outlet 

Hexavalent chrom 

mg/dscm 

0.006 

0.003 

0.009 

0.006 

kg/hr 

2.35x10"* 

1.38X10"4 

3.59X10"4 

2.44X10"4 

tium 

mg/Ah 

0.004 

0.002 

0.006 

0.004 

% Efficiency* 

99.993 

99.995 

99.994 

"Efficiencies are calculated from mass emission rates (kg/hr), and the average is based on averaging efficiencies for each, run. 

^During Run 3 at Inlet B, it was suspected that the probe may have contacted the duct wall. Therefore, the values obtained for Run 3 at Inlet B 

were not used to calculate averages or efficiency. 
P.46 

2.80 kg/hr (6.18 lb/hr). Hexavalent chromium emissions at 

inlet A averaged 140 mg/dscm (0.061 gr/dscf), or 2.99 kg/hr 

(6.59 lb/hr). At the inlet B location, total chromium emissions 

averaged 1.46 mg/dscm (6.38 x IO"4 gr/dscf), or 0.024 kg/hr 

(0.053 lb/hr). Hexavalent chromium emissions at inlet B averaged 

1.52 mg/dscm (6.66 x IO"4 gr/dscf), or 0.025 kg/hr (0.056 lb/hr). 

The relatively high inlet loadings observed during this test are 

more than likely attributable to the large tank capacities and 

the large number of parts being plated during the test. 

Emissions measured at the outlet of the packed-bed 

scrubber/mesh-pad mist eliminator system averaged 0.006 mg/dscm 

(3.0 x 10"6 gr/dscf) for both total and hexavalent chromium, or 

2.5 x 10"4 kg/hr (5.5 x 10"4 lb/hr) for total chromium and 

2.4 x 10"4 kg/hr (5.4 x 10"4 lb/hr) for hexavalent chromium. The 

removal efficiency of the control system averaged 99.99 percent. 

The average total current applied to the six electroplating tanks 

during outlet testing was 374,700 Ah. Therefore, the process 

emission rate, based on total and hexavalent chromium 

measurements, was 0.004 mg/Ah (6.2 x IO"5 gr/Ah). 

4.1.3.5 Discussion of Packed-Bed Scrubber/Mesh-Pad Mist 

Eliminator Performance. As discussed in Section 4.1.3.3, 

recirculation sprays to the composite mesh pad were shut down 

during testing to help increase the exhaust rate. During 

emissions testing and for a period of time following the tests, 

only periodic washdown of the composite mesh pad was used. A few 

months after the unit was tested, an increase in pressure drop 

was observed, indicating that the composite mesh pad was plugged. 

The pad had to be taken apart and cleaned, layer by layer. Once 

the unit was put back on line, continuous irrigation of the 

composite mesh pad was initiated, and no increases in pressure 

drop have been observed in the months since. Apparently, the 

high-pressure periodic spray was not able to penetrate to the 

finer layers in the center of the pad. Continuous irrigation 

with the low-pressure wash appears to prevent the buildup of 

30 

B 45 
P.47 

chromium within these finer layers, thus eliminating the plugging 

problem. 

As shown on Tables 8a and 8b, total and hexavalent chromium 

emissions were lower at Inlet B, which services four tanks, than 

they were at Inlet A, which services two tanks. This can be 

explained by the fact that the four tanks vented by Inlet B are 

all circular tanks with depths ranging from 6 to 18 m (20 to 

60 ft). Inlet A vents two rectangular, horizontal tanks, each 

approximately 2 m (7 ft) deep. More chromium will be emitted 

when a part is electroplated in a shallow horizontal tank than 

when that part is electroplated in a deep vertical tank. In a 

shallow tank, the hydrogen gas is evolved closer to the surface 

of the plating solution and the agitation effect is much greater 

than with the hydrogen gas generated in a deeper tank. 

4.1.4 Discussion of Composite Mesh Pad Performance. 

Table 9 presents the performance data for the composite mesh 

pad systems tested at Precision Engineering, Monroe Auto 

Equipment, and Remco Hydraulics, Inc. A graphical illustration 

of the outlet concentrations for each plant is shown in Figure 3. 

The data from Monroe differentiate the tests done with a foam 

blanket present in the plating bath from the tests done without a 

foam blanket in the bath. The mesh-pad units at Monroe and 

Precision are identical in design with the exception of an 

improvement in the seal system around the pads in the unit at 

Monroe. These mesh-pad units consist of a series of three mesh 

pads with the composite pad as the second pad in the control 

system. The air pollution control unit tested at Remco consisted 

of a packed-bed scrubber followed by two mesh pads, with the 

composite mesh pad positioned first. 

The extremely high inlet concentrations measured at Remco 

resulted in a very high percent reduction for the unit compared 

to the percent reductions observed at Monroe and Precision. The 

inlet loading at Precision was lower than the other units tested 

because a moisture extractor was located prior to the inlet test 

location. Test data from another hard chromium plating facility 

31 

46 
TABLE 9. PERFORMANCE DATA FOR COMPOSITE MESH-PAD MIST ELIMINATORS 

Plant 

Precision 

Monroe, 

no foam blanket 

Monroe, 

with foam blanket 

Remco 

Chromium 

concentration, 

mq/dscm. 

Inlet 

0.278 

0.951 

0.377 

73.2 

Outlet 

0.011 

0.011 

0.008 

0.006 

Outlet 

process 

emission 

rate, mg/Ah 

0.014 

0.079 

0.041 

0.004 

Current 

loading, 

Ah 

83,500 

13,600 

18,100 

374,800 

Percent 

reduction, 

% 

95.9 

98.7 

97.5 

99.99 

OJ 

^1 
P.49 

0.03 

OUTLET CONCENTRATION, MG/DSCM 

0.025 -

0.02 

0.015 

0.01 

0.005 

-i_ 

I I I 

_1_ 

MONROE-W/O FB MONROE-W/FB PRECISION 

PLANT NAME 

REMCO 

Figure 3. Outlet chromium concentration data for composite 

mesh-pad mist eliminator systems. 

33 

48 
P.50 

indicate that moisture extractors are capable of removing 

approximately 85 percent of the chromium mist entering the 

device.11 The test data presented iri Table 9 suggest that the 

higher the inlet concentration, the greater the percent reduction 

attainable and the lower the process emission rate. On the other 

hand, regardless of the variations in the inlet loadings, the 

outlet concentration levels are relatively constant. Figure 4 

illustrates the lack of correlation between inlet loadings and 

outlet concentration levels. This suggests that outlet 

concentration levels are a better measure of the performance of 

the units than process emission rates or percent reductions. 

The relationship between inlet loading and percent reduction 

is shown in Figures 5 and 6. A regression analyses was performed 

on the data from Monroe and Precision to determine if a linear 

relationship existed between inlet loadings and control 

efficiencies. The correlation coefficients for both inlet 

concentration and inlet mass rate were very good: r=0.82 and 

r=0.85, respectively. The data from Remco were not included 

because of the excessively high inlet loadings. The data in 

Figures 4 and 5 suggest that at an inlet concentration of about 

1.2 mg/dscm, or a mass emission rate of 0.05 kg/hr, the 

dependency on inlet loadings no longer exists and the percent 

reduction is at a relatively constant level regardless of the 

inlet loading. This phenomena is expected since 100 percent 

control or greater can never be achieved regardless of the inlet 

loading. The high correlation coefficients further support the 

assumption that inlet loadings have an effect on the performance 

efficiencies of the control systems. As shown in Figure 4, 

outlet concentration levels are independent of inlet loadings, 

and so can be used as reliable indicators of control device 

performance. 

Process emission rates, mg/Ah, also are not valid measures 

of control device performance. Inlet loadings to the control 

system are strongly dependent upon the amount of current applied 

to the plating tank(s). As discussed above, the outlet 

34 

49 
Co 

On 

E 

u 

*0 

? 

c 

0 

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u 

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0.024 

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0.020 

0.018 

0.016 

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0.010 

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0.004 

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8 1 . 9 0 172 84 5 0.595 0 348 0 973 0.23 5 0.36 3 1.055 0.25 0 0 825 

Inle t concentrat I on , mg/dscm 

Figure 4. Composite mesh-pad mist eliminator data 

concentration. 

inlet vs outlet 

u 

Ol 
102 

101-1 

100 

9£ 

98 

97 

96 

95-| 

94 

% reduction = 3.62*(inlet conc, mg/dscm) + 95.46 

r = 0.81 

l-«ci:—' ' -' '— • I oTi 02 03 04 05 06 07 08 55 \ l'.1I S 10 15 20 25 M 35 40 45 50 55 60 65.7b 75 80 85 90 

Intel concentration, moMscm Inlet concentration, mgtison 

Figure 5. Composite mesh-pad mist eliminator data - efficiency versus inlet concentration. 

0 7 

% reduction = 76.6*(inlet mass rate, kg/h) + 95.74 

r = 0.83 

ados 001 0615 0.02 0.62s obs 0.635 004 0.645 1 Ti W i!i 15 Si 4 7s 5 

Iniet mass rale, kg/h Wet mass rate, kglh 

Figure 6. Composite mesh-pad mist eliminator data - efficiency versus inle t mass rate . 
P.53 

concentration levels are independent of the inlet loading. 

Therefore, it follows that the outlet concentrations are not 

dependent upon the current applied to the plating tank(s). 

Constant outlet concentrations result in high process emission 

rates for operations with low current loadings and low process 

emission rates for operations with high current loadings. - For 

example, as shown in Table 9, Remco had the highest current 

loading of the units tested (374,800 Ah). This high current 

loading produced the lowest process emission rate (0.004 mg/Ah). 

Monroe (with no foam blanket) had the lowest current loading 

(13,600 .Ah) and the highest process emission rate (0.079 mg/Ah). 

However, the outlet concentration levels for both the Remco and 

Monroe units were relatively constant (0.006 and 0.011 mg/dscm, 

respectively). Thus, process emission rates are not reliable 

indicators of control device performance. 

The data presented in Figure 3 and Table 9 might suggest 

that the unit at Remco represents a higher level of control than 

the units at Monroe and Precision. The finest material layers in 

the composite mesh pad at Remco were woven with a smaller 

diameter fiber than the material used in the composite pads in 

the Precision and Monroe units. The difference in the fiber 

diameters could have contributed to the difference in the 

performance levels. However, as noted in Section 4.1.3.5, the 

unit at Remco developed a plugging problem after a few months of 

use. Even though the problem has been corrected, and the unit 

has been operating without any increase in pressure drop, some 

concern still exists regarding the long term maintenance 

requirements for this unit. In addition, the outlet emission 

levels are very low for all the units, and some data overlap 

exists between the outlet concentration levels measured at Remco 

and those measured at Monroe when a foam blanket was present in 

the plating bath. Therefore, the data from all three composite 

mesh-pad systems tested were determined to represent one control 

level. 

37 

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P.55 

TABLE 10. CHROMIUM ELECTROPLATING AND CHROMIC ACID ANODIZING 

TANK SPECIFICATIONS AT THE NAVAL AVIATION DEPOT, 

ALAMEDA, CALIFORNIA 

Type/ Dimensions, Capacity, 

Tank No. (l,w,d) , m (ft) L (gal)a 

5,00 0 

(1,320 ) 

5,00 0 

(1,320 ) 

8,720 

(2,300) 

2,62 0 

(690) 

2,62 0 

(690) 

2,62 0 

(690) 

2,62 0 

(690) 

8,14 0 

(2,150 ) 

4,09 0 

(1,080 ) 

Hard chromium 

1 

2 

3 

4 

5 

6 

7 

Chromic acid 

8 

9 

platina 

anodizin 

2.4, 

(8.0, 

2.4, 

(8.0, 

4.3, 

(14.0, 

1.8, 

(6.0, 

1.8, 

(6.0, 

1.8, 

(6.0, 

1.8, 

(6.0, 

q 

4.9, 

(16.0, 

2.4, 

(8.0, 

1.2, 

4.0, 

l.:2, 

4.0, 

1.2, 

4.0, 

0.9, 

2.8, 

0.9, 

2.8, 

0.9, 

2.8, 

0.9, 

2.8, 

1.2, 

4.0, 

1.2, 

4.0, 

1.8 

6.0) 

1.8 

6.0) 

1.8 

6.0) 

1.8 

6.0) 

1.8 

6.0) 

1.8 

6.0) 

1.8 

6.0) 

1.5 

5.0) 

1.5 

5.0) 

1 Assumes a free board space of 15 cm (6 in.) 

39 

54 
P.56 

All of the plating and anodizing tanks are equipped with 

heating and cooling systems to maintain uniform solution 

temperatures. Overhead hoists are used to transport parts in and 

out of the plating and anodizing tanks. 

4.2.2 Air Pollution Control.12'

14 

Each of the plating and anodizing tanks is equipped with 

double-sided draft hoods. Three identical control systems are 

used to control chromium emissions from the plating and anodizing 

tanks. Each control system consists of a vertical-flow, single 

packed-bed scrubber unit with chevron-blade mist eliminators 

preceding and following the scrubber. The packed-bed scrubberunits were installed by Viron International Corporation* in 1990. 

Following treatment in these units, the gas streams are ducted to 

fiber-bed mist eliminators. Figure 7 presents a schematic of a 

typical fiber-bed mist eliminator. 

Three of the hard chromium plating tanks (1 through 3) are 

commonly ducted to one control system. The remaining four 

plating tanks (4 through 7) are commonly ducted to a second 

control system, and the two anodizing tanks (8 and 9) are 

commonly ducted to. a third control system. For purposes of 

discussion, the control systems will be designated as Line G 

(anodizing tanks), Line L (three plating tanks), and Line M (four 

plating tanks). The ventilation rates for Lines G, L, and M are 

680 actual m3/min (24,000 actual ft3/min), 700 actual m3/min 

(24,800 actual ft3/min), and 400 actual m3/min 

(14,300 actual ft3/min), respectively. 

The fiber-bed mist eliminators, manufactured by CECO 

Filters, Inc. and installed in 1990, are located on the roof of 

the plating shop. Booster fans are used following each packedbed scrubber to aid in maintaining the appropriate gas flow rate 

Mention of trade names or commercial products is not 

intended to constitute endorsement or recommendation for 

use. 

40 

55 
P.57 

I H Gas 

EH§ Liquid 

1 I Coarse Fiber Drainage Layer 

Fine Fiber Collection Layer 

V "-S-"'- ' Oli*!.V''*'"''*' " V" . - a* r 

Liquid 

Out 

Figure 7. Schematic of a typical fiber-bed mist eliminator. 

41 

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P.59 

(2.5 gal/hr) for the larger units on lines G and L, and at a rate 

of about 4.7 L/hr (1.3 gal/hr) for the smaller unit on line M. 

4.2.3 Process Conditions During Testing.12 

4.2.3.1 Exhaust Line G. Four four-hour chromium emissions 

test runs were performed at the outlet of the control unit on 

exhaust line G, which ventilates two chromic acid anodizing 

tanks. During the testing period, one of the tanks contained 

four aluminum sheets, each with a surface area of 3.4 m2 

(36.5 ft2). The other tank contained one aluminum sheet with a 

surface area of 3.4 m2 (36.5 ft2) and a row of (unspecified) 

parts. Average total current applied to the two anodizing tanks 

during testing ranged from 4,000 to 5,100 Ah. 

4.2.3.2 Exhaust Line L. Two three-hour and one four-hour 

emission test runs were conducted at the outlet of the control 

unit on line L, which ventilates three hard chromium plating 

tanks. During the tests, each of the tanks contained four parts 

to be electroplated, and each part had a surface area of 0.7 m2 

(7.6 ft2). Average total current applied to the three tanks 

during testing ranged from 29,400 to 42,600 Ah. 

4.2.3.3 Exhaust Line M. Line M pulls air from four hard 

chromium plating tanks. One eight-hour emission test run was 

performed at the outlet of the fiber-bed mist eliminator 

controlling the line. In addition, two four-hour emission test 

runs were performed simultaneously at the inlet and outlet of the 

fiber-bed mist eliminator. During the tests, each tank contained 

four small parts, each with a surface area of 0.1 m2 (1.5 ft2 ). 

Current applied to the four tanks during inlet testing ranged 

from 37,400 to 37,600 Ah. The current ranged from 37,400 to 

37,600 Ah for the outlet test runs that were conducted in 

conjunction with the inlet runs. The current applied to the tank 

during the eight-hour run at the outlet was 75,100 Ah. 

4.2.4 Results of Emissions Testing.12 

Table 11 presents the performance data for each of the 

fiber-bed mist eliminator scrubber systems tested at the Naval 

Aviation Depot. Emissions measured at the outlet of the fiber43 

58 
Run 

No. 

TABLE 11. PERFORMANCE DATA FOR THREE SCRUBBER/FIBER-BED MIST ELIMINATOR SYSTEMS 

AT THE NAVAL AVIATION DEPOT, ALAMEDA, CAUFORNIA.11 

Inlet total chromium emissions" Outlet total chromium emissions 

Process 

current, Ah 

mg/dscm 

(IO'3) 

kg/hr 

(IO'3) 

mg/Ah 

(IO"3) 

Process 

current, Ah 

mg/dscm 

(IO-3) 

kg/hr mg/Ah 

(IO-3) 

< 0.004 

< 0.004 

< 0.005 

<0.005 

< 0.005 

<0.007 

0.019 

<0.005 

<0.010 

0.011 

< 0.004 

< 0.003 

<0.006 

(IO"3) 

<4.1 

<4.4 

<3.9 

<4.2 

<4.1 

<0.7 

<1.9 

<0.4 

<I.O 

1.2 

<0.4 

<0.3 

<0.6 

% Efficiency0 

rf*-

1 

2 

3 

4 

AVG 

1 

2 

3 

AVG 

1 

2 

3 

AVG 

37,600 140 

37,400 200 

37,500 170 

4.14 

5.31 

4.73 

Exhaust Line G 

. 

i 

JL 

2< 

2< 

4: 

32 

M 

75,100 

440 37,600 

567 37,400 

504 50,000 

3,990 

3,990 

5,100 

5,100 

4,540 

Exhaust Line L 

29,400 

29,400 

42,600 

33,800 

Exhaust Line M 

0.083 

0.086 

0.104 

0.109 

0.095 

0.127 

0.374 

0.097 

0.199 

0.358 

0.112 

0.099 

0.190 

99.9 

99.9 

99.9 

aEach emission control system controls a ventilation exhaust line. Line G exhausts emissions from chromic acid anodizing tanks; lines L and G 

each exhaust emissions from hard chromium plating tanks. 

''No inlet testing was performed on the control units for lines G or L. For line M, two emission test runs were conducted between the packedbed scrubber and the fiber-bed mist eliminator. 

cEfficiencies are calculated from mass emission rates (kg/hr), and the average is based on averaging efficiencies for each run. 

so 
P.61 

bed mist eliminator system controlling exhaust line G averaged 

9.5 x IO"5 mg/dscm (4.2 x IO"8 gr/dscf), or <0.5 x IO"5 kg/hr 

(<1.1 x IO"5 lb/hr). The average total current applied to the 

anodizing tanks exhausted to line G was 4,540 .Ah, resulting in a 

total chromium process emission rate of <4.l x 10 mg/Ah 

(<6.3 x IO"5 gr/Ah). No inlet measurements were made at lj.ne G 

and, therefore, no removal efficiencies could be determined. 

At the outlet of the control system for line L, emissions 

averaged 2.0 x 10"4 mg/dscm (8.7 x IO"8 gr/dscf), or 

<1.0 x IO"5 kg/hr (<2.2 x IO"5 lb/hr). The average total current 

applied to the tanks exhausted by line L was 33,800 Ah. 

Therefore, the total chromium process emission rate from the 

control system was <1.0 x IO"3 mg/Ah (<1.5 x IO"5 gr/Ah). As 

with line G, there was no inlet testing performed. 

For line M, emissions were measured between the packed-bed 

scrubber and the fiber-bed mist eliminator. These measurements 

are representative of inlet conditions for the fiber-bed mist 

eliminator and averaged 0.17 mg/dscm (7.4 x IO"5 gr/dscf), or 

4.73 x IO"3 kg/hr (10.4 x IO"3 lb/hr). Emissions measured at the 

outlet of the fiber-bed mist eliminator averaged 

1.9 x IO"4 mg/dscm (8.3 x IO"8 gr/dscf), or <0.6 x IO"5 kg/hr 

(<1.3 x IO"5 lb/hr). The removal efficiency of the fiber-bed 

mist eliminator averaged 99.9 percent. The average total current 

applied to the tanks serviced by Line M during outlet testing was 

50,000 Ah. Therefore, the outlet total chromium process emission 

rate was <6.0 x IO'4 mg/Ah (<9.3 x IO"6 gr/Ah). 

4.2.5 Discussion of Fiber-Bed Mist Eliminator Performance. 

There were no adverse operational factors identified during 

emissions testing of the fiber-bed mist eliminators at the 

Alameda Facility. The control devices performed well, and the 

emission testing demonstrated that fiber-bed mist eliminators are 

capable of achieving outlet chromium concentrations of 

3.7 x 10"4 mg/dscm (1.6 x 10"7 gr/dscf) or less. 

Figure 8 is a graphical presentation of the outlet chromium 

concentration levels measured from each of the three fiber-bed 

45 

60 
P.62 

OUTLET CONCENTRATION, MG/DSCM (1E-04) 

2 -

" a 

I . I i 

LINEM LINEL LINEG 

Figure 8. Fiber-bed mist eliminator outlet concentrations, 

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P.64 

OUTLET CONCENTRATION. MG/DSCM (1E-4) 

I 

LINEM LINEL LINEG 

Figure 9. Fiber-bed mist eliminator outlet concentrations 

without high test values. 

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P.66 

0.03 

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OUTLET CONCENTRATION, MG/DSCM 

A > TRADrriONAL SCRUBBERS 

B - COMPOSITE MESH PAD • MONROE W/O FOAM BLANKET 

C . COMPOSITE MESH PAD - MONROE W/FOAM BLANKET 

D . COMPOSITE MESH PAO • PRECISION ENGINEERING 

E • COMPOSITE MESH PAD - REMCO HYDRAULICS 

FM . FIBER-BED MIST ELIMINATOR - ALAMEDA/UNE M 

FL • FIBER-BED MIST ELIMINATOR • ALAMEDA/UNE L 

FG • FIBER-BED MIST ELIMINATOR - ALAMEOA/LINE G 

-©- -©- -©-

B D E 

PLANT CODE 

FM FL FG 

Figure 10. Performance data for mist eliminator systems, 

50 

65 
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TABLE 12. PARAMETERS FOR THE HARD CHROMIUM ELECTROPLATING MODEL PLANTS 

OS 

^2 

Model operation 

Plant Size 

Small Medium Large 

Operating time, hr/yr 

Percent time electrodes 

energized, percent 

Total ampere-hours per year, 

Ah/yr 

2,000 

70 

5.0 x 106 

3,500 

70 

42 x IO6 

6,000 

80 

160 x IO6 

Number of tanks 

Tank dimensions (l,w,d), m (ft) 

Ventilation rate per tank, 

m

J

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Uncontrolled hexavalent chromium 

emission rate, kg/yr (lb/yr) 

Number of operations nationwide 

1 

3.6, 1.1, 1.8 

(12.0, 3.5, 6.0) 

297 (10,500) 

50 (110) 

1,080 

4 

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2 ® 3.6, 1.2, 1.8 

(12.0, 4.0, 6.0) 

7.6,0.9, 1.8 

(25.0, 3.0, 6.0) 

57 (2,000) 

2 @ 170 (6,000) 

531 (18,750) 

420 (926) 

310 

8 

2 ® 1.2, 1.2, 3.0 

(4.0, 4.0, 10.0) 

4 ® 3.6, 1.2, 1.8 

(12.0, 4.0, 6.0) 

2 ©7.6,0.9, 1.8 

(25.0, 3.0, 6.0) 

2 @ 57 (2,000) / 

4 ® 170 (6,000) 

2 ©531 (18,750) 

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P.70 

TABLE 13. HEXAVALENT CHROMIUM EMISSION ESTIMATES ASSOCIATED WITH 

THE USE OF PACKED-BED SCRUBBERS AND NEW EMISSION CONTROL 

TECHNOLOGIES AT HARD CHROMIUM ELECTROPLATING MODEL PLANTS 

Emission estimates, kg/yr (lb/yr) 

Small Medium Large 

Uncontrolled 

Single packed-bed scrubber* 

Mist eliminator with mesh pads in series 

Packed-bed scrubber/mesh-pad mist 

L. 

eliminator system" 

Fiber-bed mist eliminator 

50(110) 

0.5(1.1) 

0.10(0.22) 

0.10(0.22) 

0.10 (0.22) 

420 (926) 

4.2 (9.3) 

0.84(1.85) 

0.84(1.85) 

0.84(1.85) 

1,600(3,530) 

16 (35.3) 

3.20 (7.06) 

3.20 (7.06) 

3.20 (7.06) 

a

Single packed-bed scrubber that reduces uncontrolled emissions by 99 percent. 

"-"New control technology that reduces uncontrolled emissions by 99.8 percent. 

54 

1 6U 
TABLE 14. ANNUAL ENERGY REQUIREMENTS ATTRIBUTABLE TO THE USE OF PACKED-BED 

SCRUBBERS AND NEW EMISSION CONTROL TECHNOLOGIES AT HARD CHROMIUM 

PLATING MODEL PLANTS 

Small Medium Large 

u. 

Operating parameters 

Total ventilation rate, m/min (ftJ/min) 

Operating time, hr/yr 

Basic capture svstem 

Number of fans 

Individual fan sizes, hp 

Total fan size, hp 

Electrical use, kWh/yr 

Control Device 

Packed-bed scnibber 

Number of control devices 

Individual fan sizes, hp 

Total fan size, hp 

Increase in energy requirement over basic capture system to operate fans, hp 

Individual pump sizes, hp 

Total pump size, hp 

Total additional energy requirement, hp 

Increase in electrical use over basic capture system alone, kWh/yr* 

Mist eliminator with mesh pads in series 

Number of control devices 

Individual fan sizes, hp 

Total fan size, hp 

Increase in energy requirement over basic capture system to operate fans, hp 

Increase in electrical use over basic capture system alone, kWh/yr8 

340 

(12,000) 

2,000 

1 

10 

10 

14,900 

1 

15 

15 

5 

1.5 

1.5 

6.5 

9,700 

1 

25 

25 

15 

22,400 

990 

(35,000) 

3,500 

1 

40 

40 

104,400 

I 

60 

60 

20 

3.0 

3.0 

23 

60,100 

1 

100 

100 

60' 

156,700 

2,000 

(70,000) 

6,000 

2 

2 @ 40 

80 

358,100 

2 

2 ® 60 

/ 120 

^40 

2 ® 3.0 

6.0 

46 

205,900 

2 

2 ® 100 

200 

120 

537,100 

(continued) 

o 
TABLE 14. (continued) 

Small Medium Large 

in 

cr» 

Packed-bed scrubber/mesh-pad mist eliminator svstem 

Number of control devices 

Individual fan sizes, hp 

Total fan sizes, hp 

Increase in energy requirement over basic capture system to operate fans, hp 

Individual pump sizes, hp 

Total pump size, hp 

Total additional energy requirement, hp 

Increase in electrical use over basic capture system alone, kWh/yr8 

Fiber-bed mist eliminator 

Number of control devices 

Individual fan sizes, hp 

Total fan size, hp 

Increase in energy requirement over basic system to operate fans, hp 

Increase in electrical use over basic capture system alone, kWh/yr* 

1 

30 

30 

20 

3 

3 

23 

34,300 

1 

40 

40 

30 

44,800 

1 

100 

100 

60 

7.5 

7.5 

67.5 

176,200 

1 

125 

125 

85 

221,900 

2 

2 ® 100 

200 

120 

2 ® 7.5 

15 

135 

604,300 

2 

2 ® 125 

250 

170 

760,900 

aNumbers were rounded to the nearest 100 kWh. 
P.73 

37.3 MWh/yr for the small model plant to 895 MWh/yr for the large 

model plant. This range represents an increase of approximately 

150 percent over the uncontrolled level and approximately 52 to 

59 percent over the energy required to operate a typical packedbed scrubber. 

The total energy required to operate a packed-bed_ 

scrubber/mesh-pad mist eliminator system ranges from 49.2 MWh/yr 

for the small model plant to 962 MWh/yr for the large model 

plant. This is an increase of approximately 170 to 230 percent 

compared to the uncontrolled level and approximately 71 to 

100 percent compared to using a typical packed-bed scrubber. 

For fiber-bed mist eliminators, the total energy 

requirements range from 59.7 MWh/yr for the small hard chromium 

plating model plant to 1,120 MWh/yr for the large model plant. 

This is an increase of approximately 210 to 300 percent over the 

uncontrolled (basic capture system alone) level and approximately 

98 to 140 percent over the energy requirements for operating a 

typical packed-bed scrubber. 

5.3 Wastewater Impacts 

Use of each of the three new emission control technologies 

for hard chromium plating operations results in the generation of 

wastewater that requires reuse, treatment, or disposal. However, 

based on available information, it is assumed that all wastewater 

generated by the control devices can be drained to the plating 

tanks to make up for evaporation losses, as is typically the 

practice with other control technologies currently used in the 

industry. 

5.4 Solid Waste Impacts 

One potential source of solid waste from hard chromium 

plating operations is the sludge produced by wastewater treatment 

operations. As noted in the previous section, wastewater 

generated by the three new control technologies for hard chromium 

plating is assumed to be recirculated and reused in the process. 

This recirculation minimizes the wastewater treatment throughput, 

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TABLE 15. SOLID WASTE IMPACTS ASSOCIATED WITH THE USE OF PACKED -

BED SCRUBBERS AND NEW EMISSION CONTROL TECHNOLOGIES 

AT HARD CHROMIUM ELECTROPLATING MODEL PLANTS 

P.75 

Hard chromium plating model plants 

Small 

0.82 (29) 

10 

0.08 (2.8) 

0.95 (34) 

5 

0.19(6.7) 

2.3 (81) 

1.1 (39) 

10 

5 

0.45 (16) 

2.1 (74) 

5 

0.42(15) 

Medium 

2.1 (74) 

10 

0.21 (7.4) 

2.6 (92) 

5 

0.52 (18) 

6.7 (237) 

3.3(117) 

10 

5 

1.3(46) 

6.4 (226) 

5 

1.3 (46) 

Large 

4.2(148) 

10 

0.42 (15) 

5.2 (184) 

5 

1.0(35) 

13 (459) 

6.7 (237) 

10 

5 

2.6 (92) 

13 (459) 

5 

2.6 (92) 

Single packed-bed scrubbers 

3 3 Total volume of packing material, m (fr) 

Frequency of replacement, yr 

Annualized volume, m3/yr (ft/yr) 

Mist eliminators with mesh pads in series 

Total volume of mesh pad material, nr (ft3) 

Frequency of replacement, yr 

Annualized volume, nr/yr (fr/yr) 

Packed-bed scrubbers/mesh-pad mist eliminator svstems 

Total volume of packing material, n r (ft3)

3 

Total volume of mesh pad material, m3(ft3) 

Frequency of replacement of packing material, yr 

Frequency of replacement of mesh pads, yr 

Annualized total volume of material, m3/yr (fr/yr) 

Fiber-bed mist eliminators 

Total volume of packing material, m (fr) 

Frequency of replacement, yr 

Annualized volume, nr/yr (fr/yr) 

--Based on a packing-bed depth of 0.9 m (3 ft) 

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TABLE 16. CAPITAL COSTS OF SINGLE PACKED-BED SCRUBBERS AND NEW CONTROL 

TECHNOLOGIES FOR NEW AND EXISTING HARD CHROMIUM ELECTROPLATING 

MODEL PLANTS (NOVEMBER 1988 DOLLARS)5'

1 6"18 

Model plant size 

Small Medium Large 

Control technology New Existing New Existing New Existing 

Single packed-bed scrubber 

Mesh-pad mist eliminator with 

mesh pads in series 

Packed-bed scrubber/mesh-pad 

mist eliminator system 

Fiber-bed mist eliminator 

36,700 

27,200 

58,100 

114,600 

45,900 

34,000 

72,600 

126,100 

74,200 

71,800 

97,800 

228,600 

92,800 

89,800 

122,200 

251,500 

148,400 

143,600 

195,600 

502,800 

185,500 

179,500 

244,500 

688,300 

a-* 

^1 

^1 
TABLE 17. NET ANNUALIZED COSTS OF SINGLE PACKED-BED SCRUBBERS AND NEW 

CONTROL TECHNOLOGIES FOR NEW AND EXISTING HARD CHROMIUM ELECTROPLATING 

MODEL PLANTS (NOVEMBER 1988 DOLLARS)5'

16"18 

Control technology 

Single packed-bed scnibber 

Mesh-pad mist eliminator with 

mesh pads in series 

New 

9,700 

13,500 

Small 

Existing 

11,100 

14,900 

Model plant size 

Medium 

New 

18,600 

32,800 

Existing 

21,500 

36,400 

New 

38,800 

76,700 

Larce 

Existing 

44,600 

84,100 

Packed-bed scrubber/mesh-pad 

mist eliminator system 

17,000 19,300 31,800 35,700 72,100 80,000 

o-* 

NJ 

Fiber-bed mist eliminator 28,900 30,700 66,200 69,800 149,200 156,300 

oo 
compared to the capital costs of single packed-bed scrubbers 

installed at new or existing plants. 

As shown in Table 17, the net annualized costs of ..operating 

this control technology are $13,500 to $76,700 for new plants, 

and $14,900 to $84,100 for existing model plants. For new 

plants, the costs are 40 to 100 percent higher than the costs of 

operating single packed-bed scrubbers; for existing plants, the 

costs are 30 to 90 percent higher. 

5.5.2 Packed-Bed Scrubber/Mesh-Pad Mist Eliminator System. 

As shown in Table 16, capital costs of installing packed-bed 

scrubber/mesh-pad mist eliminator systems are $58,100 to $195,600 

for new model plants, and $72,600 to $244,500 for existing model 

plants. These costs are from 30 to 60 percent higher than the 

capital costs associated with the installation of single packedbed scrubbers at these model plants. 

Table 17 shows that the net annualized costs of operating 

packed-bed scrubber/mesh-pad mist eliminator systems range from 

$17,000 to $72,100 for new model plants, and $19,300 to $80,000 

for existing model plants. For new plants, the operating costs 

are 70 to 90 percent more than the costs associated with the use 

of single packed-bed scrubbers. For existing plants, the 

operating costs are 70 to 80 percent higher. 

5.5.3 Fiber-Bed Mist Eliminators. 

As shown in Table 16, the model plant capital costs of 

fiber-bed mist eliminators for new plants are approximately 

$114,600 to $457,100. This is approximately 210 percent more 

than the capital costs of $36,700 to $148,400 for single packedbed scrubbers. For existing plants, single packed-bed scrubber 

capital costs range from $45,900 to $185,500, and fiber-bed mist 

eliminator costs are $126,100 to $502,800, a difference of about 

170 percent. 

Table 17 shows that the net annualized costs for single 

packed-bed scrubbers at new plants range from $9,700 to $38,800. 

Net annualized costs for fiber-bed mist eliminators in these same 

plants are $28,900 to $149,200, an increase of about 200 to 

63 

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TABLE 18. ESTIMATED PERCENT CHANGE IN HARD CHROMIUM ELECTROPLATING COST OF 

THREE END PRODUCTS ATTRIBUTABLE TO VARIOUS CONTROL TECHNOLOGIES (1988 DOLLARS)19 

Percent price increase, % 

Control technology 

Automobiles 

model plant size 

small medium large 

Industrial rolls11 

model plant size 

small medium large 

Hydraulic cylinders"--

model plant size 

small medium large 

a. 

a. 

Composite mesh-pad mist 

eliminator 

Packed-bed scrubber/mesh-pad 

mist eliminator system 

Fiber-bed mist eliminator 

Single packed-bed scrubber 

12.5 3.9 3.4 10.9-18.3 3.3-5.6 2.1-3.5 18.0-36.0 5.6-11.1 3.5-7.1 

16.1 3.8 3.2 14.1-23.6 3.3-5.5 2.0-3.4 23.5-46.4 5.5-10.9 3.4-6.8 

25.9 7.3 6.1 22.7-38.1 6.3-10.5 3.8-6.3 37.4-74.9 10.5-21.0 6.3-12.6 

9.4 2.4 2.0 8.3-13.9 2.1-3.5 1.2-2.1 13.6-27.3 3.5-6.9 2.1-4.1 

"Ranges include percent increases in electroplating costs at $0.009/cnr to $0.06/cm2 ($0.06/in.2 to $0.40/in.*') 

Ranges include percent increases in electroplating costs at $0.005/cm2 to $0.009/cm2 ($0.03/in. to $0.06/in. ) 

OO 
P.83 

2 percent for large plants to 27 percent for small plants. 

Estimates of the changes in final product prices 

attributable to increases in electroplating costs when new 

control technologies are used are presented in Table 19. The 

final products are hard chromium-plated parts for a 

representative automobile and a typical backhoe using hardchromium- electroplated hydraulic cylinders. As stated in 

Table 19, price increases for industrial roll end products can 

not be easily estimated because of their wide diversity. 

However, for most industrial rolls, the cost of electroplating is 

less than 10 percent of the final product price, and use of the 

new control technologies would increase the price of the end 

products by less than 1 percent.19 

6.0 CONCLUSIONS/SUMMARY 

In terms of performance, composite mesh-pad systems and 

fiber-bed mist eliminators achieved higher performance levels 

than those achieved by packed-bed scrubbers. The performance 

levels for fiber-bed mist eliminators were higher than those for 

composite mesh-pad systems. However, the economic impacts 

associated with the use of fiber-bed mist eliminators are much 

greater than the impacts attributable to the use of either 

composite mesh-pad systems or traditional packed-bed scrubbers. 

Furthermore, the economic impacts presented for fiber-bed mist 

eliminators were based only on costs of the fiber-bed mist 

eliminator itself. As discussed in Section 4.3, the relatively 

high performance level of the fiber-bed mist eliminator was due, 

in part, to the inlet load reduction attributable to the use of 

the coarse control system upstream of the fiber-bed mist 

eliminator. If the costs for the upstream control system were 

included in the cost of control for fiber-bed mist eliminators, 

the economic impact would be even greater, particularly for small 

businesses. The economic impacts for composite mesh-pad systems 

are not significantly different than those for traditional 

packed-bed scrubbers. 

67 

82 
TABLE 19. ESTIMATED CHANGE IN PRICE OF FINAL PRODUCTS ATTRIBUTABLE TO THE 

INCREASE IN HARD CHROMIUM ELECTROPLATING COSTS WHEN USING VARIOUS CONTROL 

TECHNOLOGIES (1988 DOLLARS)19 

cn 

oo 

Estimated price increase, $ 

Control technology 

Automobiles" 

model plant size 

small medium large 

Industrial rolls0 

model plant size 

small medium large 

Hydraulic cylinders- backhoe0 

model plant size 

small medium large 

Composite mesh-pad mist 

eliminator 

Packed-bed scrubber/mesh-pad 

mist eliminator system 

Fiber-bed mist eliminator 

Single packed-bed scrubber 

13.22 4.09 2.61 

17.04 4.02 2.50 

27.48 7.70 4.68 

10.00 2.54 1.52 

24.80 

31.97 

7.59 

7.46 

4.81 

4.60 

51.55 14.29 8.62 

18.76 4.71 2.80 

"Price increases are based on a representative automobile, the Oidsmobile Cutlass/Ciera (six model years in the 1980's). 

''Amount of price increase for final products cannot be readily estimated for industrial rolls. The electroplating cost as a percentage of 

the price of the final product can differ for rolls with the exact same plating costs because of variations in roll thickness (not plating 

thickness) prior to plating or in the quality of the steel substrate. Industrial rolls themselves are an intermediate, rather than a final, 

product. 

cFinal product costs are based on a representative backhoe with 11 hydraulic cylinders and a list price of $37,000. 

GO 
P.85 

1 mt .-i mf " 

The composite mesh-pad systems are economically viable 

control options for all sizes of hard chromium electroplating 

operations, as indicated by the increased use of these systems. 

The use of fiber-bed mist eliminators, on the other hand, is 

limited to a few, very large hard chromium electroplating 

operations. It appears that, of the two new emission .control 

techniques, composite mesh-pad systems represent the more 

reasonable approach to controlling emissions of chromic acid mist 

from all hard chromium plating'operations. 

7.0 REFERENCES 

1. CECO Aerosol Fiber Bed Filters and Systems for the 

Collection or Recovery of Mists and Valuable Solids. 

Product Information Brochure. 1987. CECO Filters, Inc., 

Conshohocken, Pennsylvania, p. 2. 

2. Memo from Barker, R., MRI, to Smith, A., EPA:ISB. November 

12, 1990. Report of meeting with Kimre, Inc., May 10, 1990. 

3. Holmes, T.L. and G.K. Chen. Design and Selection of 

Spray/Mist-Elimination Equipment. Chemical Engineering. 

October 15, 1984. p. 86. 

4. Telecon. Cassidy, M., MRI, with Kaulius, S., CECO Filters, 

Inc., Conshohocken, Pennsylvania. February 6, 1992. 

Information regarding fiber-bed mist eliminators. 

5. Chromium Emissions from Chromium Electroplating and Chromic 

Acid Anodizing Operations- Background Infonnation Document 

for Proposed Standards. Preliminary Draft. December 1990. 

6. Hexavalent Chromium Emission Test Report: Precision 

Engineering, Seattle, Washington. Advanced Systems 

Technology, Atlanta, Georgia. Prepared for U.S. 

Environmental Protection Agency, Research Triangle Park, 

North Carolina. EMB Report 91-CEP-18. December 1991. 

7. Emission Test Report: Emission Test Results for Total 

Chromium Inlet and Outlet of the South Fume Scrubber. 

Monroe Auto Equipment, Hartwell, Georgia. IEA, Research 

Triangle Park, North Carolina. Report No. 192-92-25. 

February 1992. 

8. Telecon. Cassidy, M., MRI, with Moorehead, D., Monroe Auto 

Equipment, Hartwell, Georgia. March 10, 1992. Process 

information pertaining to the December 1991 chromium 

emissions test at Monroe Auto Equipment. 

69 

1 84 
P.86 

' * 

9. Telecon. Cassidy, M., MRI, with Brooks, A., KCH Services, 

Inc., Forest City, North Carolina. March 17, 1992. 

Information regarding the mesh-pad mist eliminator system 

tested at Monroe Auto Equipment? 

10. Chromium Electroplaters Emission Test Report: Remco 

Hydraulics, Inc., Willits, California. Advanced Systems 

Technology, Atlanta, Georgia. Prepared for U. S... 

Environmental Protection Agency, Research Triangle Park, 

North Carolina. EMB Report 91-CEP-17. June 1991. 

11. Chromium Electroplaters Test Report: Roll Technology 

Corporation, Greenville, South Carolina. Peer Consultants, 

Dayton, Ohio. Prepared for U. S. Environmental Protection 

Agency, Research Triangle Park, North Carolina. EMB Report 

88-CEP-13. August 1988. 

12. Chromium Emission Test Results: Building 32 Plating 

Facility BAAQMD Authority to Construct: 574 Naval Aviation 

Depot, Alameda. Naval Energy and Environmental Support 

Activity, Port Hueneme, California. Prepared for Western 

Division, Naval Facilities Engineering Command. 

NEESA 2-176. UIC: 65885. May 1991. 

13. Memo from Barker, R., MRI, to Mulrine, P., EPA/ISB. 

January 14, 1992. Site visit report: Naval Aviation Depot, 

Alameda, California. 

14. Telecon. Cassidy, M., MRI, to S. Kaulius, CECO Filters, 

Inc., Conshohocken, Pennsylvania. October 31, 1991. 

Information about design of fiber-bed mist eliminator units. 

15. Tower Packing and Internals Including Mist Eliminators. 

Glitsch, Inc., Dallas, Texas. Bulletin No. 217, 3rd ed., 

1975, pp. 7-8. 

16. Memorandum from Barker, R., MRI, to Smith, A., EPA/ISB. 

Summary of Fiber-Bed Mist Eliminator Cost Data for the Hard 

Chromium Plating Model Plants. December 28, 1989. 

17. Memorandum from Barker, R. and Shrager, S., MRI, to 

Vervaert, A., EPA/ISB. Summary of Mesh-Pad Mist Eliminators 

with Mesh Pads in Series Cost Data for the Hard Chromium 

Electroplating Model Plants. February 1, 1991. 

18. Memorandum from Barker, R., and Shrager, S., MRI, to 

Vervaert, A., EPA/ISB. Summary of Packed-Bed Scrubber/MeshPad Mist Eliminator System Cost Data for the Hard Chromium 

Electroplating Model Plants. February 1, 1991. 

70 

85 
P.87 

A . ' -'• 

S* 

19. Memo with attachment from Watkins, T., EPA/SDB, to Barker, 

R., MRI. April 15, 1992. Transmittal of' economic analysis 

document, Economic Impact Assessment of Emerging 

Technologies for Controlling Chromium Emissions from 

Chromium Electroplating Operations. 

71 

§ 86