Integrated Vapor Collection Unit and Low NOx RTO Design For a Chemical Tank Loading / Unloading Station
Executive Summary
Epcon delivered a custom-engineered integrated emissions-control solution for a chemical storage and loading/unloading terminal: combining a central vapor-collection unit (bladder tank), an automated control and safety system, and a regenerative/thermal oxidizer (RTO) designed for low-NOₓ operation and high VOC destruction. This integrated design significantly reduces capital and operating costs compared to traditional full-capacity flare/oxidizer systems, while achieving high destruction-removal efficiency (up to 99.99 %) and ensuring compliance with stringent air-quality regulations.
Project Overview
A major chemical-distribution terminal in Texas expanded its capacity and required a modern vapor management system to handle emissions from storage tanks and loading/unloading racks. These emissions arise from both “standing losses” (tank vapors during idle/unloading) and “working losses” (vapor release during active liquid transfer). Epcon was contracted to design, fabricate and commission an integrated vapor-collection + RTO emissions-control system — to capture vapors centrally, buffer variable vapor loads, safely oxidize the collected vapor stream, and minimize fuel use and operating costs.
The Challenge
The facility faced several interlinked issues:
- Variable and intermittent vapor generation: Tank vapour emissions fluctuate — low emissions during idle periods (standing losses), but rapid, high-volume vapor release during loading/unloading (working losses). This variability makes sizing a fixed-capacity oxidizer inefficient and costly.
- Regulatory compliance under strict emission rules: The terminal must meet air-quality regulations (e.g. for VOCs / HAPs), even during periods of low vapor release — requiring a system able to treat both peak and low-flow emissions reliably.
- High operating fuel & cost burden: Traditional continuous-operation oxidizers or flares demand constant fuel/assist gas, even when vapor streams are low — an inefficient and expensive approach under idle periods.
- Safety concerns due to flammable vapor handling: Vapors from chemical tank unloading can be highly volatile. Uncontrolled release, incomplete combustion, or flashback could present serious risk. The system had to incorporate safety features such as LFL-monitoring, flame arrestors, controlled vapor release, and automated interlocks.
- Flexibility and energy efficiency: The terminal needed a solution that isn’t over-designed for maximum instantaneous load, but optimized for average and intermittent loads — in order to conserve energy/fuel, reduce operating cost, and lower environmental footprint.
Engineering Requirements
To meet these challenges, Epcon defined a comprehensive design specification:
- A central vapor-collection (bladder) tank to aggregate vapors from all storage tanks, loading/unloading racks, and container-filling stations. The tank must have: floating-bladder mechanism, level sensors, pressure instrumentation, and the ability to buffer vapors for 4–7 hours before release. This enables decoupling of vapor generation events from oxidizer operation.
- Controlled and automated vapor release logic: Using level/pressure sensors and a control system to trigger discharge of collected vapors to the oxidizer only when a certain volume or concentration threshold is reached — reducing unnecessary oxidizer run time during low emissions.
- A Regenerative Thermal Oxidizer (RTO) sized according to average expected vapor loads (not peak extremes), capable of destroying VOCs/VOC-laden vapors, compliant with regulatory standards, and achieving high destruction removal efficiency (DRE) — up to 99.99%.
- Low-NOₓ burner configuration: To minimize nitrogen-oxide emissions across all firing capacities, aligning with environmental and regulatory requirements.
- Safety features and explosion prevention: Including flame arrestors, detection of lower-flammability-limit (LFL) via monitoring, dilution-air control to avoid flammable mixtures, blocking valves, temperature-control interlocks. All vapors are collected and held in a controlled vessel prior to release — avoiding continuous open lines of vapor.
- Flexibility and reliability: The system must handle intermittent emissions, variable vapor loads, and permit scheduled maintenance — without compromising compliance or safety.
The Solution
Epcon delivered an Integrated Vapor Collection + RTO System with the following key components:
- A central bladder-type vapor-collection unit — aggregate vapors from all tanks and loading/unloading racks to a pooled vapor buffer, rather than routing each source to the oxidizer directly. The bladder tank includes sensors for liquid/vapor level and pressure monitoring to control vapor intake and output.
- An automated control system: when vapor concentration or volume in the collection tank reaches preset thresholds, the system triggers release of vapors to the RTO; otherwise the RTO remains idle — conserving fuel during idle periods. This ensures efficient operation under variable load.
- A Regenerative Thermal Oxidizer with ceramic-bed heat recovery, optimized for low-NOₓ burner operation, designed to destroy VOCs / hydrocarbons / solvent vapors at high efficiency (DRE up to 99.99%) when vapors are discharged.
- Safety & flammability-control features: flame arrestors, inlet-air dilution control, LFL monitoring — protecting against flashback or explosion risks when dealing with volatile tank vapors.
- Energy-efficient operation and fuel savings: Because the RTO is operated only when vapors are present (buffered via bladder tank), the facility avoids continuous fuel use for oxidation — reducing fuel consumption and operating costs compared to a full-capacity oxidizer sized for worst-case peak flows. According to Epcon’s data, this design achieved up to 50% capital cost reduction compared to conventional full-capacity designs.
- Turnkey delivery and integration: Epcon managed engineered design, fabrication, instrumentation/control, installation, commissioning and startup — delivering a ready-to-use, fully compliant vapor-management system.
Technical Specifications
Vapor Collection Unit: Bladder-type central tank collecting vapors from storage tanks, loading/unloading racks, filling stations
Vapor Buffering Capacity: Holds vapor for 4–7 hours before release to oxidizer — decoupling generation events from treatment.
Exhaust Treatment: Regenerative Thermal Oxidizer (RTO) — ceramic-bed regenerative heat recovery, low-NOₓ burner, designed for VOC/solvent vapor destruction
Destruction Efficiency (DRE): Up to 99.99% VOC destruction during compliance testing.
Emissions Treated: Tank vapors (standing & working losses), hydrocarbon/solvent vapors from loading/unloading & storage tanks
Safety / Controls: LFL monitoring, flame arrestors, dilution-air control, inlet flow control, pressure/level sensors, automated logic — minimizing explosion/flashback risk.
Operating Mode: Standby / idle mode during low/no vapor release; full oxidation cycle during vapor discharge events — efficient energy usage.
Fuel/Energy Efficiency: Lower fuel consumption vs. continuously-operating oxidizer sized for peak loads; energy savings via optimized operation.
Delivery Scope: Engineering design, fabrication, controls, instrumentation, installation support, commissioning — turnkey delivery by Epcon
The Results
The integrated vapor-collection + RTO system delivered significant value, including:
- Major capital cost savings (~ 50 %) compared to conventional full-capacity oxidizer or flare systems sized for worst-case emissions scenarios.
- High emission-destruction efficiency (DRE up to 99.99 %), ensuring regulatory compliance and safe exhaust of solvent and chemical vapors.
- Substantial fuel and operating cost reduction: Because the oxidizer runs only when vapors are released, and stays idle otherwise, fuel consumption is minimized — improving operational economics and sustainability.
- Increased operational flexibility: The vapor buffer decouples emission events from oxidizer operation, allowing the terminal to manage variable loading/unloading schedules without over-sizing equipment.
- Improved safety and reduced risk: Integrated safety systems — LFL monitoring, flame arrestors, controlled vapor release — reduce flashback or explosion risk associated with handling volatile vapors.
- Simplified emissions-control infrastructure: A central collection + single RTO replaces multiple individual vapor-control units, lowering complexity, maintenance, and footprint.
Lower environmental footprint & energy use: Efficient VOC destruction and optimized fuel usage reduce emissions (VOCs, NOₓ) and energy consumption per unit of throughput.
Why Epcon Chose an Integrated Vapor-Collection + RTO Approach
- Efficiency across variable load conditions: Many chemical storage/terminal operations have intermittent emissions (idle, loading, unloading), so buffering vapors in a central tank before treatment avoids the inefficiency of over-sized oxidizers.
- Regulatory & environmental compliance with minimized resource use: High DRE combined with low-NOₓ burners and controlled operation helps meet tightening air-quality standards while reducing fuel use and operating cost.
- Safety-first design for volatile chemical vapors: Use of vapor buffers, LFL monitoring, flame arrestors, and controlled release significantly reduces risk of flashback or uncontrolled combustion, critical in chemical terminals.
- Cost-effectiveness and scalability: Lower capital and operational cost compared to traditional systems; system can be scaled or duplicated as terminal throughput grows — ideal for expanding distribution terminals.
- Sustainability & energy savings: Regenerative RTO with possible heat recovery reduces net energy consumption and emissions, aligning with modern ESG / sustainability goals and tighter environmental regulations.
Contact Epcon
Epcon specializes in designing, fabricating, and supplying integrated vapor-collection and air-pollution control systems — including bladder-tank vapor collection units, RTOs, safety-engineered control systems, and turnkey installation for chemical storage, loading/unloading terminals, and distribution sites.
Contact Epcon engineering team to assess your terminal’s vapor-emissions profile — we can tailor a vapor-collection + oxidation solution to meet your regulatory, safety, and cost-efficiency needs.
