### 1

MEMORANDUM

TO: Tina Ndoh, U.S. EPA/OAQPS/SPPD

– Minerals and Manufacturing Group

FROM: Eastern Research Group, Inc.

DATE: June 4, 2014

SUBJECT: Comparison of 40 CFR Part 60, subpart U (Standards of Performance for the

Phosphate Fertilizer Industry: Superphosphoric Acid Plants) and 40 CFR Part 63, subpart AA (National Emission Standards for Hazardous Air Pollution from Phosphoric Acid Manufacturing Plants)

This document presents a general comparison between the applicability, definitions, emission

s tandards, monitoring and operating requirements , and testing and compliance requirements of

NSPS 40 CFR Part 60, subpart U

, and NESHAP 40 CFR Part 63, subpart AA (hereafter referred
to as subpart U

, and subpart AA , respectively)

. Subpart U was last amended on October 17, 2000
and subpart AA was last amended on April 20, 2006. This document does not encompass
recordkeeping or reporting requirements: each subpart reference s the respective general
provisions.

1.0 PROCESS DESCRIPTION FOR PRODUCING SUPERPHOSPHORIC ACID

Superphosphoric acid (SPA) is produced by further concentrating merchant grade phosphoric
acid (54 percent P 2 

### O 5 

### ) to approximately 70 percent P 2 

### O 5



### . 1 

### The acid is usually concentrated using
vacuum evaporation.

2.0 COMPARISON OF NSPS 40 CFR PART 60, SUBPART U TO NESHAP 40 CFR PART 63, SUBPART AA

The following sections provide a brief comparison of sub part U to subpart AA standards for phosphoric acid manufacturing

.

2.1

. Applicability

Both sub part U and subpart AA apply to SPA operations ; however, subpart AA also applies to

wet

- process phosphoric acid (WPPA) process lines and purified acid process lines

. While NSPS
40 CFR Part 60, s ubpart T applies to WPPA plants, there does not appear to be any NSPS standards appl icable to purified acid process lines

. Because sub part U only applies to SPA plants,

the remaining sections of this document do not discuss WPPA or purified acid process lines. The

1 Both subpart U and subpart AA specify the concentration of P 2 O 5 in SPA as greater than 66 percent by weight.

### 2

applicability of each subpart to SPA is presented in Table 2.1. S ubpart U r eferences design capacity, while subpart AA applies to major sources.

Table 2.1. Applicability Provisions in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpart AA

40 CFR Part 60, Sub part U 40 CFR Part 63, Subpart AA

Each SPA plant [a] having a design capacity of more

than 15 tons P 2 O 5 feed per calendar day [§60.2 1 0 (a)] Each phosphoric acid manufacturing plant [§63.600(a)], including the following new or existing affected sources at a phosphoric acid manufacturing plant:

Each evaporativ e coolin g tower [§63.600(b)(2)]

Each phosp hate rock dryer [§63.600(b)(3)]

Each phosphate rock calciner [§63.600(b)(4)]

Each superphosphoric ac id process line [a]

[§63.600(b)(5)]

Does not apply to a new or existing phosphoric acid manufacturing plant this is not a major source [§63.600(c)]

No R&D exemption Includes R&D exemption [ §63.6 00 (d) ]

No SSM exemption Includes SSM exemption [ §63.600 (e) ]

[ a ] For both sub part U and subpart AA

, requirements apply to evaporators, hot wells, acid sumps, and cooling tanks

. [ b ] 40 CFR Part 60, subpart T applies to WPPA plants.



### 2. 2. Definitions

S ub part U defines a n SPA plant. S ubpart AA define s a n SPA process line . H owever, the
definition of an SPA plant in subpart U specifically states that an SPA plant is a facility that

concentrates acid “

for eventual consumption as a fertilizer

. ” Subpart AA does not include this
specific condition in the definition of a n SPA proce ss line. Subpart AA also includes several

additional definitions related to S PA manufacturing

. Refer to Table 2.2 for details.

Table 2.2. Definitions in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpart AA

40 CFR Part 60 , Sub part U 40 CFR Part 63, Su bpart AA

S PA plant: any facility which concentrates WPPA to 66 percent or greater P 2 O 5 content by weight for eventual consumption as a fertilizer . [§60.2 11 (a)] S PA process line: any process line which concentrates WPPA to 66 percent or greater P 2 O 5 content by weight . [§63.601] Definitions in Subpart AA related to S PA manufacturing n ot in Sub part U Evaporative cooling tower: an open water recirculating device that uses fans or natural draft to draw or force ambient air through the device to

remov e heat from process water by direct contact. [§63.601]

### 3

2. 3. Standards

Sub part U contains a single standard for total fluorides from a n S PA plant

. Subpart AA contains
total fluoride standards for new and existing S PA process lines . Separate standards apply to
vacuum evaporation and submerged combustion processes at existing sources

. 2 

### As presented in
Table 2.3, subpart AA also includes standards for evaporative cooling towers.

Table 2.3. Standards in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpar t AA

HAP/Pollutant 40 CFR Part 60,

Sub part U 40 CFR Part 63, Subpart AA

Existing Sources New Sources

Total Fluorides (lb/ton of equivalent P 2 O 5 feed) Affected Facility: 0.010 [§63.212(a)] SPA Process Line

Vacuum Evap

. Process: 0.010 [§63.602(b)(1)]

Submerged C ombustion: 0.20 [§63.602(b)(2)] SPA Process Line:

0.00870 [§63.603(b)]

None Specified NA Prohibition on introduction of wet scrubber liquid effluent into any evaporative cooling tower. [§63.602(e) and §63.603(e)]



### 2.4

. Monitoring and Operating Requirements

The most substantial difference s between sub part U and subpart AA in regards to monitoring and
compliance is related to establishing and adhering to parameter monitoring ranges for wet
scrubbing systems. Both subparts include re quirements to operate a continuous parameter
monitoring system to record pressure drop, but only subpart AA includes a requirement to
monitor and record the flow rate of scrubbing liquid. Subpart AA also includes specific
requirements that facilities must operate within the establish parameters : such requirements are

not included in sub part U

. Refer to Table 2.4 for details.

Table 2.4. Monitoring and Operating Requirements in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpart AA 40 CFR Part 60, Sub part U 40 CFR Part 63, Subpart AA

P 2 O 5 Feed Accounting

– S PA Plant/Process Line

 Install, calibrate, maintain, and operate a monitoring device which can be used to determine the mass flow of phos

- bearing feed to process within an accuracy of ±5% over operating range. [§60.2 1 3 (a) ]

 Maintain a daily record of eq. P 2 O 5 feed according to procedures in subpart. [§60.2 1 3 (b) ]  Install, calibrate, maintain, and operate a monitoring

device which can be used to determine and permanently record the mass flow of phos

- bearing feed to process within an accuracy of ±5% over operating range. [§63.6 0 5(a) (1) ]

 Maintain a daily record of eq. P 2 O 5 feed according to procedures in subpart. [§63.6 0 5(b) (1) ]

2 Based on industry responses to the April 2010 Section 114, only one manufacturer is permitted to use a submerged combustion process for the prod uction of SPA, although that process was indefinitely shutdown on June 1, 2006.

### 4 Table 2.4. Monitoring and Operating Requirements in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpart AA 40 CFR Part 60, Sub part U 40 CFR Part 63, Subpart AA Scrubbing Systems Install, calibrate, maintain, and operate a monitoring device which continuously measures and permanently records the total pressure drop across the process scrubbing

system (accuracy of ± 5% over operating range). [§60.2 1 3 (c) ] Install, calibrate, maintai n, and operate a monitoring system which continuously measures and permanently

records:

A) the pressure drop across [§63.6 0 5(c)(1)] , and

B) the flow rate of scrubbing liquid to [§63.6 0 5(c)(2)]

,

Each scrubber in the process scrubbing system in

15

- min block averages (accuracy of ± 5% over operating range). [§63.6 0 5(c) (1) and (c)(2) ]

Establish allowable ranges, maintain daily averages within the established ranges, for pressure drop and flow rate. [§63.6 0 4 and §63.6 0 5( d )]



### 2.5

. Testing and Compliance

The testing and compliance requirements vary in frequency and method between sub part U and
subpart AA

. Sub part U only requires an initial performance test, whereas subpart AA requires
initial and annual testing. Subpart AA also allows facilities a broader choice of test methods than

sub part U in determining P 2 

### O 5 

### content of feed.

Table 2.5. Testing and Compliance in 40 CFR Part 60, Subpart U and 40 CFR Part 63, Subpart AA

40 CFR Part 60, Sub part U 40 CFR Part 63, Subpart A A Frequency of Performance Test

Within 60 days of max production rate, but no later than 180 days after initial startup [§60.8] Existing Sources : On or before applicable compliance

date and then annually

. [§63.6 0 6(a)(1)]

New Sources: Within 180 days of compliance date and

then annually

. [§63.6 0 6(a)(2)] Sampling and Analysis Methods

Total Fluorides: Method 13A or 13B with at
least a 60 minute sampling time and

0.85 dscm (30 dscf) sample volume. [§60.2 1 4(b)(2)]

P 2 O 5 Content of Feed : The Association of Official Analytical Chemists (AOAC) Method

9. [§60.2 1 4(b)(3)(ii) ] Total Fluorides: Method 13A or 13B with a t least a

60 minute sampling time and 0.85 dscm (30 dscf) sample volume. [§63.6 0 6(c)(2)]

P 2 O 5 Content of Feed: Various methods from t he Association of Florida Phosphate Chemists, Seventh

Edition 1991

. [§63.60 6(c ) (3) (ii) ]