SCAQMD – Nitric Acid Tanks Rule

South Coast Air Quality Management (SCAQMD or District) Governing Board adopted Rule 1159.1 for the control of nitrogen oxides (NO_X) emissions from nitric acid units. Rule 1159.1 is expected to impact over 900 nitric acid units across nearly 250 facilities.

Background

Under California Assembly Bill 617 (AB 167), Air Districts designated as nonattainment for one or more air pollutants were required to adopt an expedited schedule by January 2021 for the implementation of Best Available Retrofit Control Technology (BARCT)¹ by December 31, 2023. As facilities begin to transition out of the Regional Clean Air Incentives Market (RECLAIM), SCAQMD identified the need for a command-and-control regulation to control NO_X emissions from nitric acid units in line with BARCT requirements.

Nitric acid units are typically found at metal finishing, precious metal reclamation, or expanded graphite foil production facilities. NO_X emissions are generated from the either a chemical reaction between the nitric acid and metals or from thermal decomposition of the nitric acid.

Nitric Acid Unit Requirements (Rule 1159.1(d)(1))

Nitric acid units vented to an air pollution control device (APCD) will be subject to the following requirements:

• Limit overall NO_X emissions from the combined nitric acid unit(s) vented to an APCD to 0.30 pounds per hour (lb/hr) [Rule 1159.1 (d)(1)(A)(i)]; or
• Achieve a 99% control efficiency [Rule 1159.1 (d)(1)(A)(ii)].

Facilities that elect to comply with the performance standards of Rule 1159.1(d)(1)(A)(i) or (ii) by operating an APCD that uses a scrubber solution are required to install and operate the following:

• A flowmeter to measure flowrate of scrubber solution across each stage of the APCD,
• A pH meter to measure pH of scrubber solution across each stage of the APCD, and
• A pressure differential measuring device to measure pressure drop across each stage of the APCD.

Facilities are required to monitor and record the parameters listed above at least once weekly.

Facilities that operate two or more APCD that elect to demonstrate compliance with the 0.30 lb/hr NO_X limit [Rule 1159.1 (d)(1)(A)(i)] must limit NO_X from all nitric acid units vented to an APCD across the facility to no more than 0.90 lb/hr, as demonstrated by a source test.

Alternative Compliance Pathways (Rule 1159.1(d)(2))

Facilities that operate nitric acid tanks not vented to an APCD can elect to comply with one of the following alternative compliance pathways:

• Limit NO_X emissions from all nitric acid units that are not vented to an APCD to 0.60 lb/hr, as demonstrated by a source test [Rule 1159.1 (d)(2)(A)]; or
• Demonstrate that nitric acid additions in no more than one of the past five calendar years, including the current calendar year, are less than the following [Rule 1159.1 (d)(2)(B)]:
  • 550 gallons adjusted to 68 weight percent per nitric acid unit per calendar year, and
  • 1,650 gallons adjusted to 68 weight percent for all nitric acid units electing to comply with Rule 1159.1 (d)(2)(B) per calendar year.

Facilities electing to comply with (d)(2)(A) must maintain specification sheet for each of the following:

• Product or part processed in the nitric acid unit specifying the precise concentration or maximum concentration of metal(s) present; and
• Processes conducted in the nitric acid unit specifying the type of metals processed, and the acceptable operating conditions for nitric acid concentration and processing time.

Facilities electing to comply with (d)(2)(B) must maintain the following records for at least five years:

• Record for each addition of nitric acid including
  • Date of addition,
  • Volume of the addition (in gallons),
  • Highest concentration of nitric acid based on the manufacturer’s safety data sheet or chemical analysis of a sample, and
  • Volume of addition adjusted to 68 percent by weight.

Source Testing

Prior to conducting a source test to demonstrate compliance with one of the pathways previously identified, facilities must submit a source test protocol to SCAQMD for approval. Source tests must be conducted no later than five calendar years from the last source test that demonstrated compliance with the requirements of Rule 1159.1. Final source test reports must be submitted within 120 days after the test was completed and no later than the applicable due dates listed in Table 1, Table 2, or paragraph (h)(5) of Rule 1159.1.

Labeling Requirements

By July 1, 2025, facilities with nitric acid units will need to label each unit with the tank name (or functionally equivalent identifier) and SCAQMD Application/Permit Number.² Cleaning tanks must also be labeled with “Rule 1159.1 Cleaning Tank”.

The implementation schedules for the various compliance pathways are summarized in the following tables.

What’s Next?

Rule 1159.1 is not a one-size-fits-all rule. Facilities have multiple pathways they can take to meet their compliance obligations. ALL4 can work with facilities to develop a roadmap to understand new regulatory requirements, plan for compliance, prepare emissions test plans, review emissions test data, obtain vendor quotes for new emissions control, and prepare permit applications to maximize operational flexibility. If you are interested in learning how this rule may affect your facility, please contact your ALL4 project manager or Michael McHale at 610.422.1131 or mmchale@all4inc.com.

¹Under Section 40406 of the California Health and Safety Code BARCT is defined as “an emission limitation that is based on the maximum degree of reduction achievable, taking into account environmental, energy, and economic impacts by each class or category of source.”

²Unless the nitric acid unit is subject to the labeling requirements of SCAQMD Rule1426 (f)(5) or Rule 1469 (g)(3).