





Date:		May 2012

Subject:	Secondary Impact Analysis -- SCR
		Nitric Acid NSPS Review
      EPA Contract No. EP-D-11-084; Work Assignment No. 0-01  
        RTI Project No. 02103199.000.001

From:			Melissa Icenhour
							
To:			Nathan Topham
        OAQPS/SPPD/MICG (D243-02)
        U. S. Environmental Protection Agency
      Research Triangle Park, NC  27711
      

As part of the NSPS Review for Nitric Acid Plants, it is estimated that 5 newly constructed nitric acid production units and 1 modified nitric acid production unit will become subject to the regulation in the next five years. See memo entitled Impacts of Nitric Acid NSPS Review -- NOX (Updated Memo for Final NSPS) dated May 2012 in Docket No. EPA-HQ-OAR-2010-0750.
 
The purpose of this memo is to estimate the secondary impacts of installing a selective catalytic reduction (SCR) control device on the modified production unit. The SCR will ensure that the modified source is able to meet the final emission rate of 0.50 lb nitrogen oxides (NOX) per ton 100% nitric acid (0.50 lb NOX/ton acid) under Part 60, Subpart Ga.

The secondary impacts from the installation of an SCR include an increase in facility operating costs due to the increased electricity needed to operate the SCR. The increased electricity use leads to an increase in air pollutants such as NOX, sulfur dioxide (SO2), and carbon dioxide (CO2).


There is no known power equation specific to an SCR used to control NOX emissions from a nitric acid production train. However, according to EPA's Air Pollution Control Cost Manual -  -  (EPA Cost Manual), the amount of power consumed by an SCR used to control emissions from a utility boiler can be estimated using the following equation:


      P=0.105*QBNOXin ηNOX+0.5ΔPduct+ ntotalΔPcatalyst  		Eq. 1 	

where:
P 	=	power (kW)
QB 	=	boiler heat input (MMBtu/hr)
NOXin 	= 	concentration of NOX into the SCR (lb NOX/MMBtu)
ηNOX 	=	destruction efficiency of the SCR
ΔPduct 	=	pressure drop across ductwork (inches H2O)
ntotal 	=	number of layers in the SCR
ΔPcatalyst 	=	pressure drop across catalyst (inches H2O)
 

Equation 1 can be used to estimate the power requirement for an SCR installed on a nitric acid production train if we make some assumptions about the content of the gas entering the SCR.
According to EPA Method 19, the molar heat content of natural gas is 8,710 dry standard cubic feet (dscf) per million Btu (MMBtu).
According to the ICR from Agrium North Bend, the flow rate is 24,734 standard cubic feet per minute (scfm). Assuming minimal moisture content, this is 1,484,040 dscf per hour. Also according to the ICR, the SCR at the Agrium North Bend plant has 6 catalyst layers.
Table 1 contains actual data compiled by CRI Catalyst Company to show how much pressure drop is associated with the ductwork connecting the SCR to the emission stream. The average pressure drop is 7 inches H2O.
Using Equation 1, the power required to operate the SCR is 123.46 kilowatts (kW).
According to the EPA Cost Manual, the cost of electricity is directly related to the amount of power required to the run the SCR, as shown by Equation 2.

		C=P*EP*OpHours							Eq. 2

where:
C	=	cost of electricity ($)
P 	=	power (kW)
EP	=	price of electricity ($/kWh)
OpHours	=	number of hours the plant operates the SCR during the year (hours)

According to the ICR, the plant operates 8,200 hours per year. The plant is operating in Ohio and according to this website (http://www.electricchoice.com/electricity-prices-by-state.php), the industrial cost of electricity was 6.06 cents per kilowatt-hour (kWh) in 2010.

Using Equation 2, the cost of electricity to operate the SCR is $61,352 per year.

According to this website (http://www.cleanerandgreener.org/resources/pollutioncalculator.html), electricity use results in the creation of other air pollutants including NOX, sulfur dioxide (SO2), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

Using the known inputs for Equation 1 and Equation 2, shown in Table 2, the secondary impacts of this SCR are shown in Table 3.

As described in the preamble to this final rule, the secondary impacts are minimal.



Table 1. Pressure Drop Across SCR units at Nitric Acid Plants
                                     Start
                                    Country
                               Capacity (mt/day)
                                    Process
                               Flue gas (Nm3/hr)
                                     Temp
                                     (C )
                                Pressure (bar)
                                 NOX in (ppmv)
                                NOX out (ppmv)
                                NH3 out (ppmv)
                                   PD (mbar)
                                      PD 
                                  (inch H2O)
                                                                           1995
South Africa
                                                                            550
Krupp Uhde
                                                                             70
                                                                            205
                                                                              1
                                                                           1500
                                                                            200
                                                                             35
 
 
                                                                           1998
Denmark
                                                                            225
Krupp Uhde
                                                                             30
                                                                            210
                                                                              3
                                                                           1200
                                                                            200
                                                                             10
                                                                             30
                                                                             12
                                                                           1999
USA
                                                                            200
Grand Paroisse
                                                                             27
                                                                            190
                                                                              6
                                                                           2000
                                                                             80
                                                                             30
                                                                              5
                                                                              2
                                                                           1999
USA
                                                                            100
Weatherly
                                                                         14,000
                                                                            166
                                                                              1
                                                                           2100
                                                                            100
                                                                             10
                                                                             20
                                                                              8
                                                                           1999
USA
                                                                            200
Girdler
                                                                           27.5
                                                                            229
                                                                              1
                                                                           4800
                                                                            400
                                                                             30
                                                                             20
                                                                              8
                                                                           1999
USA
                                                                            180
 
                                                                           21.5
450 - 515
                                                                              6
                                                                           3400
                                                                            100
                                                                             20
 
 
                                                                           1999
Malaysia
 
Cominco
                                                                         31,500
                                                                            477
                                                                              6
                                                                           1300
                                                                            130
-
 
 
                                                                           2000
Taiwan
 
Stamicarbon
                                                                         46,000
                                                                            187
6,2
                                                                           1200
                                                                            100
                                                                             35
 
 
                                                                           2000
India
 
Stamicarbon
                                                                          8,100
                                                                            200
                                                                              1
                                                                           4000
                                                                            100
                                                                            175
                                                                             10
                                                                              4
                                                                           2000
Spain
                                                                            370
Espindesa
                                                                             50
                                                                            220
3,5
                                                                           4000
                                                                            200
                                                                              5
 
 
                                                                           2001
Netherlands
                                                                           2000
Grand Paroisse
                                                                            260
                                                                            265
10,4
                                                                            250
                                                                             32
                                                                              5
                                                                             10
                                                                              4
                                                                           2003
Netherlands
                                                                           1700
Grand Paroisse
                                                                        210,000
                                                                            340
                                                                              9
                                                                            250
                                                                             32
                                                                              5
                                                                             10
                                                                              4
                                                                           2001
UK
                                                                            825
Krupp Uhde
                                                                            107
                                                                            225
6,5
                                                                           1000
                                                                             50
                                                                              5
                                                                             25
                                                                             10
                                                                           2001
UK
                                                                           1100
Krupp Uhde
                                                                        145,000
                                                                            380
11,5
                                                                            500
                                                                             50
                                                                              5
                                                                             25
                                                                             10
                                                                               

                                                                               

                                                                               
                                                                               

                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               

                                                                               

                                                                               
                                                                               

                                                                               
                                                                               
                                                                        average
                                                                             17
                                                                              7
Information from CRI Catalyst Company
Nitric acid units with Shell DeNOX System
http://www-static.shell.com/static/cri_catalyst/downloads/business/cracker_fun_june2001.pdf



Table 2. Known Values
                                    Element
                                    Source
                                     Value
Molar heat content of natural gas
EPA Method 19; Table 19-2
8,710 dscf/MMBtu
Flow rate of gas entering the SCR
ICR-Agrium North Bend
1,484,040 dscf/hr
Destruction Efficiency of SCR (ηNOX)
Engineering Judgment
0.90
Pressure drop across catalyst (ΔPcatalyst)
EPA Cost Manual
1.0 in H2O per layer
Number of catalyst layers (ntotal)
ICR-Agrium North Bend
6
Pressure drop across the ductwork (ΔPduct)
Table 1
7.0 in H2O
Uncontrolled NOX concentration
Engineering Judgment
500 ppm
Operating hours (OpHours)
ICR-Agrium North Bend
8,200 hours
Price of electricity (EP)
Electricity Choice website
6.06 cents per kWh
NOX emissions from electricity use
Cleaner and Greener website
3.3 lb per 1,000 kW
SO2 emissions from electricity use
Cleaner and Greener website
13.2 lb per 1,000 kW
CO2 emissions from electricity use
Cleaner and Greener website
1,911 lb per 1,000 kW
CH4 emissions from electricity use
Cleaner and Greener website
0.02 lb per 1,000 kW
N2O emissions from electricity use
Cleaner and Greener website
0.03 lb per 1,000 kW



Table 3. Calculated Values
                                    Element
                                    Source
                                     Value
Boiler Heat Input (QB)
(Flow rate of gas entering the SCR) / (Molar heat content of natural gas)

170.4 MMBtu/hr
Power (P)
Equation 1
123.46 kW
Total cost of electricity (C)
Equation 2
$61,400
NOX emissions from operation of SCR
                                                    Cleaner and Greener website
                                                                       0.407 lb
SO2 emissions from operation of SCR
                                                    Cleaner and Greener website
                                                                       1.630 lb
CO2 emissions from operation of SCR
                                                    Cleaner and Greener website
                                                                     235.940 lb
CH4 emissions from operation of SCR
                                                    Cleaner and Greener website
                                                                       0.002 lb
N2O emissions from operation of SCR
                                                    Cleaner and Greener website
                                                                       0.004 lb




