Refining & Petrochemical

Flare Systems for Refineries & Petrochemical Plants

Petroleum refineries and chemical processors handle high-BTU relief streams, sour gas with H2S, and wide-range relief loads that demand engineered flare tips, rigorous sizing, and continuous compliance documentation under MACT and NSPS rules.

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Refinery MACT Subpart CC Steam- & Air-Assist Designs API RP 521 / 537 Sour Gas Alloy Service Title V Documentation
Refinery MACT Compliance 40 CFR Part 63 Subpart CC requires refinery flares to operate within net heating value and steam-to-hydrocarbon limits. Over-steaming violations and elevated visible emissions each carry penalties up to $70,117/day. Discuss compliance requirements →
MACT
Subpart CC / UUU Compliant
>98%
Combustion Efficiency
2″–60″
Flare Tip Diameter Range
Steam
& Air-Assist Tip Designs
H2S
Sour Gas Alloy Service
Engineering Challenges

What Makes Refinery Flare Systems Different

Refinery and petrochemical flare headers collect relief streams from dozens of units. No two streams are alike in BTU content, flow rate, molecular weight, or H2S concentration.

High-BTU and High-Molecular-Weight Relief Streams

Refinery relief headers carry streams from crude units, vacuum towers, and catalytic crackers containing heavy fractions with high smoking tendency. Standard single-port tips cannot achieve smokeless combustion without steam or air assist sized to the specific stream MW and relief rate.

HPS Solution: Steam-assist and air-assist flare tips sized per API RP 521 for actual stream molecular weight and relief load, not generic assumptions.

Sour Gas and H2S Across the Flare Header

Refinery flare headers often aggregate streams from amine treating units, sour water strippers, and crude desalters, all containing measurable H2S. Combustion produces SO2 with health and odor impacts downwind, and high H2S concentrations require alloy selection per NACE MR0175.

HPS Solution: Sour-service alloy material specifications for pilot, burner, and tip internals. SO2 dispersion calculations included with engineering package.

Orders-of-Magnitude Flow Range

Normal refinery flare loads can be a fraction of 1% of the emergency design case. A flare sized only for the emergency blowdown will be unstable, loud, or prone to flameout at routine operating loads.

HPS Solution: Multi-tip or staged tip designs that provide stable combustion from minimum continuous flow through maximum emergency blowdown rate, per API RP 521 turndown guidance.

Steam Utility Waste and Over-Steaming

Refinery steam-assist flares consume enormous volumes of utility steam, adding cost and carbon. Over-steaming also violates Refinery MACT steam-to-hydrocarbon ratio limits and generates excessive noise. Under-steaming produces visible smoke.

HPS Solution: Optimized steam-assist tip designs with manual or automated steam control valves, flow meters, and Subpart CC steam-to-vent ratio monitoring instrumentation.

MACT Monitoring and Recordkeeping Obligations

40 CFR Part 63 Subpart CC requires continuous monitoring of net heating value, steam-to-hydrocarbon ratio (steam-assist), and visible emissions. Deficient monitoring programs are among the most common NOV triggers at petroleum refineries.

HPS Solution: Flare tip packages include CEMS-ready instrumentation provisions and documentation to support Subpart CC monitoring plan development and permit applications.
Product Lineup

Flare Systems for Refining & Petrochemical Service

Engineered for high-BTU streams, wide turndown ratios, and the continuous compliance documentation that Title V and Refinery MACT require.

HPS steam-assist and air-assist flare tip for refinery relief header service
Refinery Relief Headers / Process Vents

Steam-Assist & Air-Assist Flare Tips

Smokeless flare tips for refinery relief headers and process vent streams carrying high-BTU, high-molecular-weight hydrocarbons. Steam- or air-assist sized to actual stream composition and relief load per API RP 521 and Subpart CC limits.

CE / DRE>98%
Assist TypeSteam or Air
Tip Sizes2″ to 60″
Design StdAPI RP 521 / 537
H2S ServiceAlloy available
Lead Time4 to 10 weeks
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HPS sonic flare for high-pressure refinery compressor and process relief
Compressor Station / High-Pressure Relief

Sonic Flares

For high-pressure refinery and petrochemical relief headers where gas velocity exceeds conventional tip limits. Pressure-assisted sonic tips combust high-velocity streams without the lift-off and instability that defeat standard elevated flare performance.

CE / DRE>98%
Tip Sizes2″ to 36″
Operating ModePressure-assist
Design StdAPI RP 521 / 537
H2S ServiceAlloy available
Lead Time4 to 8 weeks
View Sonic Flares →
HPS enclosed combustor for refinery and petrochemical small vent streams and MACT process vents
MACT Process Vents / Small Vent Streams

Enclosed Combustors

For MACT-regulated process vents, wastewater treatment vents, and storage vessel vent streams at refineries and chemical plants where the permit requires no visible flame and documented DRE monitoring.

DRE>95% / 98%
Flame VisibilityNone
Flow Range5 to 2,000 scfm
Min. Combustion Temp1,600 to 2,000°F
MonitoringBFMS + Temp Logger
Lead Time8 to 16 weeks
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Applications

Where HPS Equipment Is Used in Refineries & Petrochemical Plants

Common refinery and chemical plant service points — each with distinct stream composition, BTU content, and compliance obligations.

FCC Units, Vacuum Towers & Atmospheric Distillation

Fluid catalytic cracker and distillation unit relief headers carry high-MW heavy fractions with high smoking tendency at relatively low flow rates. Steam or air assist is required to achieve smokeless combustion at the design relief rate.

Steam-assist and air-assist flare tips →

Sour Water Strippers & Amine Treating Units

Acid gas vent streams from amine regenerators and sour water strippers contain H2S and CO2 with low BTU content. Combustion produces SO2 requiring dispersion modeling; H2S levels drive alloy selection per NACE MR0175.

Sour-service air-assist flare systems →

Compressor Stations & High-Pressure Relief Headers

Refinery hydrogen compressors, recycle gas compressors, and high-pressure process relief headers generate high-velocity streams that exceed conventional flare tip velocity limits and require pressure-assisted sonic tip designs.

Sonic flares for high-pressure service →

MACT Process Vents & Wastewater Treatment

MACT-regulated process vents at chemical plants, refinery wastewater treatment units, and API separator covers require control devices achieving documented DRE with no visible flame and continuous temperature monitoring.

Enclosed combustors for MACT process vents →

Catalytic Reformers & Sulfur Recovery Units

Catalytic reformer pressure-relief and SRU tail gas vent streams are regulated under Subpart UUU, requiring 95% SO2 reduction. Low-BTU tail gas streams need supplemental fuel or specific tip design for stable combustion.

Air-assist flares for low-BTU streams →

Tank Farm & Storage Vessel Vents

Refinery crude and product storage tanks require vapor control during filling, floating-roof seal failures, and inert gas venting events. Small vent stream volumes and infrequent events make enclosed combustors the preferred control device.

Enclosed vapor combustors for storage vents →
Regulatory Compliance

Key Standards for Refinery and Petrochemical Flare Systems

StandardApplicabilityKey RequirementHPS ProductsStatus
40 CFR Part 63, Subpart CC
Refinery MACT (National Emission Standards for Petroleum Refineries)		 All existing and new flares at petroleum refineries subject to Subpart CC (major HAP sources). Net heating value at or above 270 BTU/scf; steam-assist steam-to-vent ratio below 3:1 lb/lb; continuous NHV monitoring; visible emission limits. Violations may require root-cause analysis and corrective action plans. Steam-Assist Flare Tips, Sonic Flares COMPLIANT
40 CFR Part 60, Subpart Ja
Standards of Performance for Petroleum Refineries (newer sources, after Nov 2008)		 New, reconstructed, and modified flares at petroleum refineries that commenced construction after November 7, 2008. Flare combustion zone NHV above 300 BTU/scf; operate within steam-to-vent or air-to-vent limits; no visible emissions except during upset; CEMS installation required for large flares. Steam-Assist Flare Tips, Sonic Flares, Enclosed Combustors COMPLIANT
40 CFR Part 63, Subpart UUU
NESHAP: Petroleum Refineries — Catalytic Cracking, Reforming, Sulfur Recovery Units		 Catalytic cracking unit (CCU), catalytic reformer, and sulfur recovery unit (SRU) process vents at petroleum refineries. CCU regenerator and SRU tail gas vent streams routed to control device achieving 95% SO2 reduction or outlet below 50 ppmv. Continuous monitoring of reduction efficiency required. Enclosed Combustors, Steam-Assist Flares COMPLIANT
40 CFR 60.18(c)
General Combustion Device Standards		 All flares and combustion devices used to comply with any NSPS or NESHAP rule at refining and petrochemical facilities. Net heating value at or above 300 BTU/scf; continuous pilot; no visible emissions except in specified circumstances; smokeless at normal conditions. All HPS flare products COMPLIANT
Title V Air Permit
Operating Permit for Major Stationary Sources		 All petroleum refineries and large petrochemical plants with major source HAP or criteria pollutant emissions above Title V thresholds. Facility-specific operating limits, emission factors, and monitoring requirements that may exceed federal minimums. HPS engineering documentation supports permit applications and permit compliance demonstrations. All products SITE-SPECIFIC
Engineer FAQ

Technical Questions on Refinery and Petrochemical Flare Systems

What is the difference between steam-assist and air-assist for a refinery flare tip?

Steam-assist tips inject high-pressure steam around the flare gas stream to entrain combustion air and improve smokeless performance on high-molecular-weight streams. They require a continuous steam utility and produce louder, noisier combustion. Air-assist tips use a forced-draft fan to supply combustion air at lower energy cost and noise, but are limited to lower flare gas velocities. HPS sizes both types to the actual relief stream composition and selects the assist type based on available utilities, permitting constraints, and noise limits.

How do you size a refinery flare for both routine operating loads and emergency blowdowns?

Refinery flares are sized per API RP 521 for the maximum emergency case (typically a power failure or cooling water failure scenario). Smokeless capacity is then determined by the steam or air assist system, which is sized for a fraction of the emergency load — typically the largest single-unit normal operating relief rate. If the ratio of emergency to normal flow is very large, multi-tip or staged tip designs provide stable combustion across the full range without excessive utility consumption at routine loads.

What monitoring does Refinery MACT Subpart CC require for flares?

40 CFR Part 63 Subpart CC requires: (1) continuous monitoring of flare gas net heating value using a gas chromatograph, calorimeter, or flow-weighted average composition method; (2) for steam-assist flares, continuous monitoring of the steam-to-vent ratio to confirm the ratio remains below 3:1 lb/lb; (3) visible emissions monitoring per EPA Method 22 during representative operating periods; and (4) a root-cause analysis and corrective action plan for any excess emissions event. HPS provides instrumentation provisions and documentation that supports the Subpart CC monitoring plan.

Can HPS supply a replacement flare tip only, without replacing the entire flare structure?

Yes. HPS can supply a replacement flare tip to fit an existing riser diameter and flange size. To properly size the replacement tip, we need the existing riser diameter, flange rating, current tip design flow and stream composition, and the current assist system (steam or air) capacity. A poorly matched tip replacement can perform worse than the original, so provide the process data to confirm compatibility before ordering.

What does “smokeless capacity” mean and how is it specified?

Smokeless capacity is the maximum flare gas flow rate at which the flare tip can combust the stream without producing visible black smoke, given a specific steam or air supply rate. It is determined by the tip design, the assist system capacity, and the stream molecular weight. At flows above smokeless capacity, the flame will smoke regardless of assist. HPS specifies smokeless capacity as a function of stream MW and assist rate so you can determine compliance risk at any operating condition, not just the design point.

Our flare header has high H2S from multiple sour units. What do we need to specify?

Specify the maximum H2S concentration in the flare header and the individual sour unit stream flow rates and compositions. Material selection for H2S service follows NACE MR0175/ISO 15156: HPS specifies 316L SS for wetted surfaces above 200 ppmv H2S; Incoloy 825 for pilot tube and burner internals above 500 ppmv; Hastelloy C-276 for acid gas service above 2,000 ppmv. We also include an SO2 ground-level concentration estimate for permit modeling at the design relief case H2S load.
MACT
Subpart CC Compliant
>98%
Combustion Efficiency
API
RP 521 / 537 Designed
H2S
Sour Service Material Options

A refinery flare that meets the emergency design case on paper can still fail Subpart CC every day it runs. The routine operating load, the assist system turndown, and the NHV monitoring plan are where most compliance problems actually live.

Craig Rosencutter, President, Hero Process Solutions

Tip Replacement & Upgrades

Replacing an aging steam-assist tip or upgrading to a sonic tip? Send us your existing riser diameter, stream composition, and assist system capacity. We confirm compatibility and lead time within 48 hours.

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Resources

Technical Reference for Refining & Petrochemical Applications

Data Sheets

Flare Tip & Combustor Spec Sheets

Dimensional and performance data for HPS steam-assist, air-assist, and sonic flare tips for refinery service.

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Product Page

Steam-Assist & Air-Assist Flare Tips

Smokeless flare tips sized to high-BTU refinery relief streams. Subpart CC and API RP 521 compliant with H2S alloy options.

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Product Page

Sonic Flares for High-Pressure Service

Pressure-assisted sonic tips for high-pressure refinery and petrochemical relief headers. API RP 521 / 537 designed.

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Product Page

Enclosed Combustors for MACT Process Vents

No-visible-flame combustion for MACT-regulated process vents, wastewater treatment vents, and storage vessel streams.

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Services

Aftermarket Parts & Flare Tip Replacement

Replacement flare tips, pilot assemblies, ignition components, and burner parts for existing refinery flare systems.

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Engineering Support

Talk to an HPS Engineer

Send us your flare header stream data, existing tip size, and permit requirements. We confirm equipment selection and lead time within 48 hours.

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Get a Quote

Refinery & Petrochemical Flare System Quote

Send us your flare header stream compositions, relief rates, existing riser size, and permit conditions. We confirm equipment selection and DRE compliance basis within 48 hours.

  • ✓ Steam-assist and air-assist flare tip sizing per API RP 521
  • ✓ Subpart CC / Subpart Ja compliance documentation
  • ✓ H2S sour service alloy selection per NACE MR0175
  • ✓ Smokeless capacity curve for permitting and operations

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Name

Ready to Specify Your Refinery Flare System?

Send us your flare header stream data, existing tip diameter, and permit conditions. We confirm equipment selection and lead time within 48 hours.

Request a Quote → Call +1 (918) 408-7608

Hero Process Solutions, 14842 Maple Dr, Kellyville, OK 74039