      



Date:	February 7, 2013

Subject: 	Environmental and Energy Impacts for Wool Fiberglass Manufacturing NESHAP  -  Proposed RTR Amendments
	40 CFR 63, Subpart NNN  -  Supplemental Proposal
	EPA Contract No. EP-D-11-084; EPA Work Assignment No. 1-07
	RTI Project No. 0213199.001.007

From: 		Cindy Hancy
		Dave Reeves

To: 		Susan Fairchild, EPA/OAQPS/SPPD/MMG

   I. Introduction
     
The purpose of this memorandum is to document the estimated environmental and energy impacts associated with the proposed residual risk and technology review (RTR) amendments to 40 CFR 63, Subpart NNN - Wool Fiberglass Manufacturing.  Secondary impacts include the solid waste, water, wastewater generated and the electricity required to operate air pollution control devices, as well as, the resultant greenhouse gas (GHG) emissions from controls or work practices required by the NESHAP. 

   II. Water, Wastewater, and Solid Waste Impacts
     
The EPA estimates that three gas-fired glass-melting furnaces at wool fiberglass manufacturing facilities will need to install a caustic scrubber to meet the proposed chromium compound emission limit for Subpart NNN. The water required to operate the scrubber and the solid and wastewater generated by the effluent were calculated for the three units. The 2010 information collection request, sent to all wool fiberglass manufacturers, requested that facilities provide detailed information for each control device. For scrubbers, facilities were asked to provide gas and water flow rates, liquid to gas ratios, pressure drop, wastewater generation, and several other operating parameters for each of their existing scrubbers. Appendix 1 contains a complete list of all the information EPA requested for scrubbers, however, because the majority of facilities submitted this information as confidential business information (CBI), facility responses are not included in this memo. The EPA compiled these ICR responses, and using the operating parameters (also considered CBI) of the three furnaces estimated to need caustic scrubbers, estimated the amount of water needed to operate the scrubbers, as well as the wastewater and solid waste that would be generated. The calculated impact estimates are provided in Table 1. 








      Table 1. Estimated Water and Solid Waste Impacts for Caustic Scrubbers on Furnaces

                             Impacts per facility
                            Total industry impacts 
Water flow rate into scrubber (gpm)[1]
                                                                            194
                                                                            582
Percent of scrubber water from recycled facility wastewater[1]
                                                                             60
                                                                             60
Total non-recycled water necessary (gallons per year)[2]
                                                                            41M
                                                                          123 M
Total scrubber effluent rate (gpm)[1]
                                                                            6.1
                                                                            6.1
Percent scrubber wastewater recycled[1]
                                                                             50
                                                                             50
Total wastewater generated (gallons per year)[3]
                                                                           1.6M
                                                                           4.8M
Total solid waste collected (lb/yr)[1]
                                                                        468,000
                                                                           1.4M
(1)Estimates from ICR responses. (2) Calculation: 194 (gpm) x 60 (min/hr) x 8760 (hrs/yr) x (100%-60%). (3) Calculation: 6.1 (gpm) x 60 (min/hr) x 8760 (hrs/yr) x (100%-50%).

   III. Energy Impacts and GHG Emissions from Electricity Usage

The amount of electricity required to operate a control device (i.e., caustic scrubber) was calculated using the information summarized in Table 1. The electricity costs associated with operating a scrubber derive from fan requirements to overcome the pressure drop in the column, ductwork, and other parts of the control system, and pump requirements to re-circulate the water. According to the EPA's Air Pollution Control Cost Manual, fan and pump energy requirements can be calculated by using equation 3-1 and 3-2, respectively. 
      Equation 3-1
Energyfan = 1.17 x 10-4x Gix Pe
      Equation 3-2
Energypump = 0.746 x 2.52 x 10-4 x Li x Pe
      Where Gi is the gas flow rate entering the scrubber, P is the total pressure drop, Li is the liquid flow rate entering the scrubber, P is the pressure of the pump which we assume to be 60 ft of water and e is the efficiency of the device. 

The average gas flow rate entering the scrubber for the three furnaces is 26,000 acfm, the average estimated pressure drop for the scrubber is 9.8 inches of water, and the average estimated liquid flow is 194 gallons per minute. Using equations 3-1 and 3-2 and an estimated efficiency of 0.7 for both the pump and the fan, we estimated the energy required to be 43kWh for the fan, and 3kWh for the pump. 

Energyfan = 1.17 x 10-4 x (26,000) x (9.8)0.7=43 kWh

Energypump = (0.746) x (2.52 x 10-4) x (60) x (194)0.7=3 kWh


Assuming operating hours is 8,760 per year, the total annual energy required for each scrubber is: 


46kWhrx 8,760hrsyr=403,000 kW/yr

This results in 1.2 million kWh per year (1,200 megawatts) for all three scrubbers.  We used the natural gas emission factor (in kilograms [kg]/MMBtu) from the General Stationary Fuel Combustion Sources subpart (40 CFR part 98, subpart C) of the Greenhouse Gas Reporting Rule (listed in Table 2) to estimate the secondary emissions for CO2, CH4, and N2O. 

  Table 2. Emission Factors from General Stationary Fuel Combustion Sources  
                          (40 CFR part 98, subpart C)

                                     Fuel
                                       
                                  Default CH4
                                emission factor
                                (kg CH4/MMBtu)
                          Default N2O emission factor
                                (kg N2O/MMBtu)
                                  Default CO2
                                emission factor
                                (kg CO2/MMBtu)
                                  Natural Gas
                                1.0 x 10−03
                                1.0 x 10−04
                                     53.02

Global warming potentials of 1 for CO2, 21 for CH4, and 310 for N2O (from Table A-1 to subpart A of part 98) were used to estimate CO2 equivalent emissions (CO2eq). First we converted kWh to MMBtu as follows: 
1,200,000 kWh x0.0034MMBtukWh=4,100 MMBtu

Using the values in Table 2 we estimated CH4, N20, and CO2, emissions as 4.1 kg/yr (9 lbs/yr), 0.41 kg/yr (0.9 lbs/yr), and 217,000 kg/yr (478,000 lbs/yr), respectively. We then calculated the CO2eq emissions based on the global warming potentials above as follows:

CO2eqlbyr=478,000lbCO2yr+ 21 x 9lb CH4yr+ (310 x 0.9lb N2Oyr)

This results in 478,500 lbs CO2eq per year for all three scrubbers.  
