Regulatory compliance control means meeting the emission limits specified in an EPA air permit, and every limit traces back to a specific rule: a NESHAP (National Emission Standards for Hazardous Air Pollutants) for hazardous air pollutants, an NSPS (New Source Performance Standard) for a new source category, a BACT (Best Available Control Technology) or RACT (Reasonably Available Control Technology) determination, or the monitoring conditions of a Title V permit.
NOx emission is where many permits are tightest, making the design of combustion and thermal oxidation systems especially important. PCC limits NOx formation with ultra-low NOx or low NOx burners, staged combustion, flameless oxidation, and flameless regenerative thermal oxidation, and reduces what remains with SNCR (Selective Non-Catalytic Reduction) and SCR (Selective Catalytic Reduction) systems. The table below points to PCC solutions for other regulated pollutants.
Ultra-Low NOx and Low NOx burners
Multi-stage thermal oxidation systems for wastes containing chemically combined nitrogen (N), NOx and/or N₂O, e.g. for the acrylonitrile production processes
Burner turndown typically to 10:1 on gaseous fuels and 4:1 on liquids
Multi-staged low-NOx incineration of nitrogen-bearing compounds in PCC thermal oxidizers
Flameless thermal oxidizers with thermal NOx as low as 1 ppmv and DRE above 99.9999%
Flameless regenerative thermal oxidizer (FRTO) systems, generating virtually zero NOx emissions
Flameless regenerative thermal oxidizer (FRTO) systems, generating virtually zero NOx emissions
Compliance Support:
Engineering studies that turn permit and emissions data into a compliance path
Incinerator / thermal oxidizer chamber temperature data logging as proof of compliance
Evaluation and modification of existing control units through PCC field services
Contact us by phone at (412) 655-0955 or request an engineering consultation to discuss your regulatory compliance and NOx control needs.
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Which Regulation for Which Technology and How PCC Fits
| Regulation | What It Typically Requires | Pollutants It Often Drives | Where PCC Addresses It |
|---|---|---|---|
| NESHAP (MACT Standards, Clean Air Act Section 112) | Emission limits or percent reductions for listed hazardous air pollutants, set by source category | Organic HAPs, HCl and other acid gases, metals, particulate | VOC and HAP abatement, acid gas absorbers and scrubbers, particulate matter control |
| NSPS (Clean Air Act Section 111) | Performance standards for new, modified, or reconstructed sources in listed categories | NOx, SO2, particulate, VOC | NOx control; acid gas control; particulate matter control |
| BACT (PSD, Attainment Areas) or LAER (Nonattainment Areas) Under New Source Review | Case-by-case control technology review for new major sources and major modifications | NOx, VOC, CO, particulate, SO2 | NOx control; flameless thermal oxidizers for gaseous waste streams |
| RACT (State Implementation Plans) | Reasonably available controls on existing sources in nonattainment areas | NOx and VOC, the ozone precursors | NOx control; VOC and HAP abatement |
| Hazardous Waste Combustor NESHAP | Standards for incinerators and other units burning hazardous waste | Organics, HCl and chlorine, metals, particulate, dioxins | liquid waste incineration |
| Title V Operating Permits | One permit that consolidates every applicable requirement, with monitoring, recordkeeping, and reporting | All of the above | Control systems designed with the operating parameters the permit monitors; field services for existing units |
| State and Local Nuisance Rules | Limits or complaint-driven requirements on odor | Reduced sulfur compounds, ammonia, organics | industrial odor control |
A single permit often includes several of these limits at once. A chemical plant thermal oxidizer can face a NESHAP emission limit on organic VOCs (volatile organic compounds) and/or HAPs (hazardous air pollutants), an acid gas emission limit, a CO (carbon monoxide) emission limit, a NOx limit, and a PM (particulate matter) from its BACT review. PCC designs the thermal oxidizer and pollution control equipment, e.g. an acid gas scrubber, SNCR or SCR, as an integrated system, ensuring complete compliance with the permit.
Combustion Controls: Prevent NOx First
NOx is one pollutant that combustion-based control systems can generate. Any combustion-based control device, from a thermal oxidizer to an incinerator, can generate NOx while it destroys VOCs or waste, and NOx that never forms needs no post-combustion NOx control. A typical burner flame can have hot spots above 3000°F, and even milliseconds at those temperatures can generate significant amounts of thermal NOx. NOx also forms from nitrogen bound in the fuel or waste (chemical NOx) and from fuel radicals reacting with nitrogen at the flame front (prompt NOx). PCC evaluates all three formation mechanisms when it determines whether an ultra-low NOx burner, low NOx burner, staged air, staged fuel, or multi-stage combustion system is needed to meet the limit.
Flameless oxidation removes the hot spots. PCC's flameless thermal oxidizer premixes waste gas, air, and fuel and then oxidizes the mixture in a hot ceramic bed with no flame, which is why its thermal NOx can run as low as 1 ppmv. For gaseous waste streams facing a BACT review, flameless oxidation should be considered early in the evaluation process.
Post-Combustion NOx Control: SNCR and SCR
Where fuel-bound nitrogen is present, combustion techniques alone may not meet the limit. NOx emissions when fuel bound nitrogen is present can be minimized with staged thermal oxidizer designs. PCC may then add an SNCR or SCR system, injecting ammonia or urea to reduce NOx to nitrogen and water, either as part of a thermal oxidizer system or as a stand-alone system on new or existing combustion equipment. The limit determines which system is appropriate: SNCR is applied where the required NOx reduction is in the range of 40-75%, in an ideal temperature window of 1650-1850°F. An SCR is used where a higher NOx reduction (60-90%) is required, which occurs at a lower ideal temperature window of 300-800°F. Please refer to the SNCR and SCR systems page for the full design comparison of these systems.
What PCC Needs to Evaluate Compliance Options
The permit or the draft limits
With the rule behind each one
Current emissions data or stack test results
If the source exists
Waste and fuel composition
Including chemically combined nitrogen, halogen, and sulfur content
Gas flow and temperature
At each point where control could be installed
Existing combustion and control equipment
As well as its condition
Compliance deadline
And any consent order or schedule
An engineering study uses this data to develop a compliance path, including evaluating whether an existing system can be modified rather than replaced.
