July 9, 2012 

Subject: Design Narrative 

1.0 Introduction 

This design has been proposed in order to meet the intent of the new emissions standards 

proposed by the United States Environmental Protection Agency (EPA) for the collection and 

control of process fugitive emissions. During the field visit on May, 23 2012 several point source 

emission sources were identified, these sources are tapping; casting; crushing/screening and 

skimming/slag raking. The proposed design addresses and provides solutions for each of these 

sources and describes the design intent for meeting the EPA objectives. See Appendix 1 for 

conceptual drawings outlining these solutions. All capture systems shall have a minimum hood 

face capture velocity of 300 FPM as per acceptable engineering standards.

2.0 Repairing existing direct exhaust system 

The existing ventilation system for the furnaces consists of three separate baghouses for each 

furnace and supplemental exhaust fans for other operations. Makeup air is provided through door 

openings and building infiltration. This ventilation system provides direct exhaust for the furnace 

and casting/tapping processes. This system was not originally designed for the lower temperature 

ferroalloy process, which has resulted in a lower ventilation rate of approximately 180,000 

CFM’s compared to the original rate of 250,000 CFM’s, a 30% decrease in capacity. New fans 

and motors sized for the current process will restore the existing system to the original design 

capacity. The existing fans have 1,500 HP motors, due to the lower temperatures and higher fan 

efficiencies available only 600 HP motors are required to provide 250,000 CFM of ventilation. 

The casting nests will be provided with new casting shields with a built in overhang over the 

nest, which will capture and direct emissions towards the casting hood for a total minimum 

efficiency of 90%.

To increase the capture rates for the tapping process, the tapping area will be enclosed to contain 

emissions generated during the process. The enclosure will consist of a solid floor and ceiling, 

including full height movable partitions to allow the operators access to the tap hole. The 

existing tap hole fans will exhaust emissions generated within this enclosure. An estimated total 

minimum capture efficiency of 95% is expected with these changes. 

Each crusher has its own dedicated baghouse, #1 crusher has three baghouses and #2 crusher has 

two baghouses. The baghouses are directly ducted to each crusher/screener and provide direct 

exhaust at each emission source on the equipment. A recent test report indicates that the 

functioning baghouses are running approximately 50% below design capacity at 4,320 CFM and 
7,673 CFM instead of the design capacities of 10,000 CFM and 12,000 CFM respectively. See 

Appendix 2 for a copy of the test reports. New fans/motors will be provided to bring the system 

up to the original design capacity. This additional ventilation capacity coupled with the 

secondary exhaust system outlined below will improve the total capture efficiencies at both 

crushers to a minimum of 85%. 

3.0 Installing a secondary exhaust system. 

While the improvement to the direct exhaust system will increase the capture rate of fugitive 

emissions, it is infeasible for this system to capture all of the generated emissions at each 

process. In order to increase the overall capture rate a secondary exhaust system is proposed to 

provide general exhaust. 

Our investigation showed that fugitive emissions emitted in the hot metal bay were collected in 

the roof monitors and pitched roof, as shown in the photograph below. 

A general exhaust system is proposed to exhaust all emissions collected above the rafters, 

capturing fugitives missed by the direct exhaust system. This general exhaust system will 

provide 12 air changes per hour (ACH), which in essence exhausts the entire volume of air above 

the rafters every 5 minutes. The general exhaust system in the hot metal bay was selected for 12 

ACH instead of 6 ACH due to the large emissions generated by the furnaces and skimming/slag 

raking processes. Providing 12 ACH for general exhausts requires approximately 120,000 CFM 

of fan capacity. This additional capacity can be provided at either the existing baghouses with 

larger motors/fans, or can be provided at a separate new baghouse. New ductwork will be ducted 

to three of the existing roof monitors which act as natural collection points. The remaining roof 

monitors will be removed and new skylights are proposed which will provide natural sunlight for 

illumination. This roof exhaust system is estimated to have a total minimum capture efficiency of 

90%. 

The secondary exhaust system will also capture emissions generated during the skimming/slag 

raking processes, as these occur within the middle of the hot metal bay. Any emissions generated 

by the casting process that was not captured by the direct exhaust system would also be captured 

by the secondary exhaust system. The emissions would naturally rise into the roof rafters and be 

CHU AND GASSMAN
CHU AND GASSMAN

exhausted from the roof monitors. Source control of these emissions is not possible due to the 

location of the process, as any ductwork located to capture emissions locally would interfere 

with overhead crane traffic. 

The crushing/screening area is also proposed to have a new general exhaust system. Each crusher 

will have its own dedicated general exhaust system providing 6 ACH of ventilation around the 

crusher, which is approximately 140,000 CFM each. This general exhaust system will serve to 

capture and contain emissions missed by the direct exhaust system, and will provide general 

ventilation in the area as well. As the crusher/screening equipment is the main source of 

emissions there is no need to exhaust the entire crusher/screening area. A proposed curtain wall 

will be provided between the hot metal bay and crushing/screening area to reduce cross 

contamination between the two areas and contain the fugitives within each respective area. This 

system is estimated to have a total minimum 85% capture efficiency rate. 

The proposed secondary exhaust system will be operated on an intermittent basis, because of this 

no dedicated makeup tempered supply air system is required. 

4.0 Conclusion 

The proposed design improves the existing direct exhaust system while providing a secondary 

exhaust system in order to fully capture and contain process fugitive emissions that are 

generated. The use of both a direct exhaust system and a general secondary exhaust system in 

conjunction is estimated to provide a TOTAL building capture rate of approximately 95%, 

including the tapping; casting; crushing/screening and skimming/slag raking processes. 

The field visit also witnessed the charging of the electric arc furnaces, no emissions were seen to 

be generated by the charging process. 
CHU AND GASSMAN

APPENDIX 1 – DESIGN DRAWINGS 





CHU AND GASSMAN

APPENDIX 2 – TEST REPORT
Flow Rate ACFM 7,673 Horsepower 25 2

 Yearly Hours in Operation (approx): 8322

Flow Rate SCFM 7,715 Amps 29 3

 Plant Cost per kW/hr: $0.042

Flow Rate lbs/ hr 34,560 Volts 460 Fan Operating Cost per Year: $7,109

Temperature F 41 RPM 1775 Fan Energy Usage, Megawatt Hrs/Yr 169.3

Density lbs/ ft3 0.0751 SF 1.00 Motor HP per Inch Pressure Loss 3.9

Fan Inlet Damper % open No Damper Cost per Inch of Pressure Loss, yr $1,010

Fan Inlet Velocity Pressure in H2O 0

Fan Inlet Pressure in H2O -8.2 Estimated HP @ 70% Fan Efficiency: 12.8

Fan Outlet Pressure in H2O -0.2 Fan Operating Cost per Year: $3,332

1

 Fan Static Pressure in H2O 7.4 Energy Savings per Year: $3,776

Fan Shaft Speed RPM 1050 Fan Energy Usage, Megawatt Hrs/Yr 79.3

Fan Motor Power Amps 31.0 Motor HP per Inch Pressure Loss 1.8

Fan Motor Power HP 27 Cost per Inch of Pressure Loss, yr $473

Fan Efficiency, % % 32.8

1

 Fan static pressure calculated using AMCA 203-90. (Outlet Static - Inlet Static - Inlet VP)

2

 Hour estimated based on 95% operating time 52 weeks/year.

3

 Plant cost per kW/hr based on data provided by Felman Production, Inc.

Estimated Annual Energy Cost @ 70% Fan Efficiency

January 28, 2011

Letart, West Virginia

Production Rate: Normal

Existing Annual Energy Cost (approx)

#2 Crusher Baghouse Fan (Hill Side)

Fan Operation Nameplate Fan Motor Data
Flow Rate ACFM 4,320 Horsepower 20 2

 Yearly Hours in Operation (approx): 8322

Flow Rate SCFM 4,379 Amps 24 3

 Plant Cost per kW/hr: $0.042

Flow Rate lbs/ hr 19,616 Volts 460 Fan Operating Cost per Year: $2,629

Temperature F 38 RPM 1775 Fan Energy Usage, Megawatt Hrs/Yr 62.6

Density lbs/ ft3 0.0757 SF 1.15 Motor HP per Inch Pressure Loss 1.6

Fan Inlet Damper % open No Damper Cost per Inch of Pressure Loss, yr $415

Fan Inlet Velocity Pressure in H2O 0

Fan Inlet Pressure in H2O -7.4 Estimated HP @ 70% Fan Efficiency: 6.5

Fan Outlet Pressure in H2O -0.2 Fan Operating Cost per Year: $1,688

1

 Fan Static Pressure in H2O 6.7 Energy Savings per Year: $941

Fan Shaft Speed RPM 1791 Fan Energy Usage, Megawatt Hrs/Yr 40.2

Fan Motor Power Amps 14.3 Motor HP per Inch Pressure Loss 1.0

Fan Motor Power HP 10 Cost per Inch of Pressure Loss, yr $267

Fan Efficiency, % % 44.9

1

 Fan static pressure calculated using AMCA 203-90. (Outlet Static - Inlet Static - Inlet VP)

2

 Hour estimated based on 95% operating time 52 weeks/year.

3

 Plant cost per kW/hr based on data provided by Felman Production, Inc.

Estimated Annual Energy Cost @ 70% Fan Efficiency

January 28, 2011

Letart, West Virginia

Production Rate: Normal

Existing Annual Energy Cost (approx)

#2 Crusher Baghouse Fan (Road Side)

Fan Operation Nameplate Fan Motor Data