DEC as an experienced RTO retrofit and refurbishment contractor: DEC can assess existing RTOs, including systems manufactured by other vendors, and develop revamping, retrofitting, refurbishment or rebuilding strategies aimed at extending service life, improving reliability, reducing energy consumption, increasing capacity, addressing obsolete components and supporting changing environmental or process requirements.

RTO Revamping Is an Asset-Optimization Project

An existing RTO does not necessarily need to be dismantled and replaced when performance declines or process requirements change. Depending on the structural condition, configuration, technology, regulatory position and future operating envelope, a plant may be able to recover performance through maintenance, refurbishment, retrofit or partial rebuilding.

The engineering question is therefore not simply whether the RTO is old. It is whether the existing asset has sufficient structural integrity, thermal performance, process suitability, controllability and upgrade potential to remain a reliable part of the plant.

1. Start With an Engineering Condition Assessment

A revamp should begin with a documented condition and performance assessment. The assessment should combine historical operating data, maintenance records, alarms and trips, emission results, energy consumption, pressure-drop trends and a physical inspection.

1.1 System-Level Assessment

• Mechanical condition of shells, chambers, manifolds, supports, access structures and connection points.
• Condition of refractory and mineral-fibre insulation, including hot spots, degradation, settlement and evidence of overheating.
• Ceramic media condition, plugging, cracking, crushing, shifting, collapse and pressure-drop distribution.
• Valve and damper condition, timing, sealing, actuator condition and cycle performance.
• Burner, fuel train, combustion-air and flame-safety condition.
• Fan, motor, VFD, bearings, coupling, vibration and operating point.
• PLC, HMI, instrumentation, safety logic, network architecture and obsolete components.
• Ductwork, expansion joints, flexible connections and process-air distribution.

1.2 Performance Baseline

The assessment should establish a baseline for airflow, pressure drop, temperature profiles, VOC loading, destruction performance, fuel consumption, electrical consumption, operating hours, alarms and unplanned downtime. Where possible, the baseline should distinguish process-driven variability from equipment deterioration.

1.3 Third-Party RTOs

For an RTO manufactured by another vendor, DEC should first obtain the available drawings, nameplate data, photographs, manuals, P&IDs, operating data, maintenance history and site rules. A preliminary feasibility assessment should explicitly distinguish documented information from assumptions and items requiring physical verification.

2. Revamp, Retrofit, Refurbish, Rebuild or Replace?

These terms should not be treated as interchangeable. They describe different levels of intervention and different project objectives.

2.1 Refurbishment

Refurbishment restores an existing RTO toward reliable operation by repairing or replacing worn components while retaining the core configuration. Typical work can include ceramic media replacement, gasket replacement, insulation repairs, valve servicing, burner tuning, fan maintenance and control-component renewal.

2.2 Retrofit

Retrofit introduces new technology or functionality that was not present in the original design. Examples include new PLC/HMI systems, upgraded instrumentation, VFDs, improved valve drives, new ceramic media, heat-recovery equipment, revised combustion control or modifications for changed process conditions.

2.3 Rebuilding

Rebuilding is a deeper intervention in which major subsystems are dismantled, repaired or reconstructed. It can include internal steelwork, refractory, insulation, media-support systems, valves, burners, duct interfaces and controls while retaining selected structural elements of the original RTO.

2.4 Replacement

Replacement becomes relevant when the existing structure or technology cannot economically or reliably support the required future operating envelope, or when the required modernization would approach the scope and cost of a new installation.

3. RTO Refurbishment: Restore the Existing Asset

Refurbishment is generally focused on restoring reliability and recovering lost performance without fundamentally changing the RTO architecture.

• Ceramic media inspection, cleaning or replacement.
• Refractory and insulation repair.
• Door and access-gasket replacement.
• Valve-seat, seal, actuator and linkage maintenance.
• Burner inspection, tuning and fuel-train maintenance.
• Fan, motor, bearing and VFD maintenance.
• Instrumentation replacement and calibration.
• PLC/HMI component renewal where compatible with the existing architecture.
• Repair of corroded or locally damaged steelwork where structurally acceptable.

The scope should be based on condition rather than a generic replacement list. For example, ceramic media fouling can increase resistance and reduce effective airflow, while damaged insulation can create hot spots and accelerate deterioration. These relationships are also reflected in published RTO maintenance guidance.

4. RTO Retrofit: Add New Capability to Existing Equipment

Retrofit is appropriate where the existing RTO remains structurally suitable but its capabilities need to be upgraded. Modernization can target energy, emissions, capacity, reliability, automation or process flexibility.

4.1 Controls and Automation Retrofit

Replacing obsolete PLCs, HMIs, I/O, communication interfaces and diagnostic functions can improve troubleshooting and lifecycle support without replacing the RTO shell. Modern controls can also support improved alarm logic, data logging and remote technical assistance.

4.2 Valve and Actuation Retrofit

Switching valves and dampers are critical to regenerative performance. A retrofit may address valve timing, sealing, actuation, drive technology, instrumentation or the suitability of the valve architecture for current operating conditions.

4.3 Ceramic Media Retrofit

Changing from older random or monolithic media to a different engineered ceramic configuration can target pressure drop, heat-transfer performance, fouling behaviour and usable capacity. Published industry material identifies ceramic-media design as a major factor in RTO efficiency and service life.

4.4 Heat-Recovery Retrofit

Where the process provides a useful heat sink, secondary heat recovery can be evaluated in addition to the regenerative heat exchange already inherent to the RTO. The technical and economic value depends strongly on exhaust temperature, VOC loading and the plant heat-demand profile.

5. RTO Rebuilding: Reconstruct Critical Systems

A rebuild sits between routine refurbishment and complete replacement. It is particularly relevant where the major vessel or tower structure remains serviceable but internal systems have reached the end of their useful life.

• Remove and replace degraded ceramic media and support layers.
• Rebuild refractory and insulation assemblies.
• Repair or replace internal steelwork and media-support structures.
• Replace or overhaul valves, dampers and actuators.
• Renew burners, fuel trains and combustion controls.
• Replace obsolete control hardware and instrumentation.
• Rework duct interfaces and expansion connections.
• Recommission and validate the rebuilt system against the defined performance requirements.

Deep rebuilding should be planned as an engineering project, not as a collection of isolated maintenance tasks. Interfaces between the retained and renewed components are often the critical path.

6. Ceramic Media and Heat-Exchange Performance

Ceramic heat-exchange media are central to regenerative performance. Fouling, plugging, cracking, crushing, channeling, shifting or deterioration can affect pressure drop, heat recovery, flow distribution and ultimately the usable capacity of the RTO.

6.1 Cleaning Before Replacement

Where media are physically sound, cleaning may recover performance without a full media replacement. Published RTO maintenance guidance describes dry cleaning approaches intended to remove deposits while keeping the ceramic elements intact and reducing downtime.

6.2 Replacement or Upgrade

Where media are damaged, excessively fouled or no longer appropriate for the process, replacement may be justified. Structured or engineered media can be evaluated against random packing or existing blocks, with pressure drop, thermal performance, fouling tendency, mechanical robustness and process contaminants considered together.

6.3 Channelled Honeycomb Blocks

Channelled honeycomb blocks can deliver high heat-transfer surface area, but after years of service they may become brittle, damaged, displaced or locally collapsed. Removal and repacking can therefore be a significant maintenance activity and should be included in shutdown planning.

7. Valves, Dampers and Flow-Control Systems

The regenerative cycle depends on reliable flow switching. A revamp should review valve architecture, sealing, timing, actuation, cushions, seats, linkages, pneumatic or electric drives and control logic.

A valve retrofit can be preferable to full equipment replacement when the primary structural and thermal systems remain suitable. However, the new valve arrangement must be checked against pressure pulses, leakage, cycle frequency, temperature, access and maintenance requirements.

8. Burner, Fuel and Combustion-System Upgrades

Burner performance influences fuel consumption, temperature stability and protection of the combustion chamber and ceramic media. A modernization assessment should review burner condition, fuel pressure, air-to-fuel ratio, ignition, flame detection, purge sequences and firing-rate control.

A properly tuned combustion system can recover performance without a major mechanical rebuild. Conversely, unstable combustion or excessive flame impingement can accelerate damage to refractory, insulation and ceramic media.

8.1 DEC.HBT™ Heating Burner Train

Where a fuel-fired heating system remains part of the future RTO architecture, the DEC.HBT™ Heating Burner Train can be evaluated as a complete heating and combustion package rather than as a burner-only replacement. The HBT™ architecture coordinates the burner with fuel supply, combustion air or oxygen where specifically engineered, ignition, flame supervision, control, permissives and safety functions.

For an existing RTO, burner modernization should therefore be assessed together with the fuel train, combustion-air system, chamber geometry, process airflow, VOC loading, required oxidation temperature, burner turndown, PLC/BMS architecture and operating history. Replacing a burner without reviewing these interfaces can simply transfer the original limitation to a new component.

• Startup: high thermal input may be required to overcome the thermal mass of the chamber and regenerative media.
• Normal production: burner duty should cover only the residual thermal requirement after regenerative recovery and process heat release are considered.
• Low-VOC operation: wide turndown can help bridge the gap between available process heat and the required oxidation temperature.
• Autothermal operation: where regenerative recovery and VOC oxidation heat are sufficient, main-burner demand can be reduced or stopped according to the approved operating philosophy.

DEC.HBT™ incorporates fuel isolation, combustion-air permissives, purge requirements, ignition and flame proving, fuel-pressure and valve-position supervision, modulation, high-temperature/process interlocks and defined safe-state logic. These functions should be integrated into the complete RTO control and safety architecture.

8.2 DEC.HGB™ Hot Gas Bypass for Thermal Protection

Modernization should also consider whether changes in production, solvent loading or VOC concentration peaks have moved the RTO closer to its thermal operating limit. The DEC.HGB™ Hot Gas Bypass is a safety and thermal-protection module that can automatically divert a controlled portion of hot gas around the regenerative ceramic media when defined protection conditions are approached.

HGB™ is not a normal process-treatment bypass or a substitute for upstream concentration management. Its function is to provide a controlled thermal-derating layer coordinated with temperature monitoring, alarms, interlocks, valve sequencing and the overall RTO safety philosophy. Bypass capacity, valve position, materials and setpoints are project-specific and must be established from the actual VOC chemistry, airflow, calorific load, media characteristics and thermal design.

Where the existing RTO is otherwise suitable, HGB™ can form part of a targeted retrofit rather than automatically requiring complete replacement. Where useful thermal energy is available, the bypass arrangement can also be evaluated together with DEC.ERS™ Energy Recovery Solutions.

9. PLC, Instrumentation, Diagnostics and Remote Support

Controls obsolescence can become a lifecycle constraint even when the mechanical RTO remains sound. Modern PLC/HMI platforms can improve first-out diagnostics, alarm management, data acquisition, remote connectivity and spare-parts availability.

The control upgrade should be treated as a functional-safety and process-control project, including I/O mapping, cause-and-effect review, permissives, trips, interlocks, burner management, valve sequencing, communication architecture and cybersecurity considerations.

DEC can support this lifecycle activity through DEC.TSS™ Technical Support Services and DEC.HDS™ Help Desk Services.

10. Fans, Ductwork, Pressure Drop and Process Airflow

A revamp should not focus exclusively on the oxidizer itself. Fans, ductwork, dampers and process capture systems determine the airflow presented to the RTO.

• Verify actual airflow against the original design envelope.
• Measure static pressure and investigate unexplained pressure increases.
• Review ceramic-media pressure drop by bed.
• Check fan operating point, motor loading, vibration and VFD range.
• Inspect dampers and process branches for incorrect balancing.
• Assess duct leakage, corrosion, expansion joints and flexible connections.

Media upgrades can change pressure drop and therefore fan duty. Any media or valve modification should therefore be evaluated as part of the complete airflow system rather than as an isolated component change.

11. Energy Efficiency, Heat Recovery and Decarbonisation

RTO modernization can be used as a first phase of a broader sustainability programme focused on reducing fuel demand and greenhouse-gas emissions while maintaining VOC destruction performance.

• Recover thermal efficiency through clean or upgraded ceramic media.
• Optimize burner firing and combustion control.
• Reduce unnecessary pressure drop and fan power.
• Evaluate secondary heat recovery where a useful heat sink exists.
• Consider electrification where site electrical capacity, energy source and process economics support it.
• Evaluate whether solvent recovery could replace destruction for recoverable VOC streams.

11.1 Full-Electric and Hybrid RTO Modernization

Electrification can be approached as a complete conversion or as a staged energy strategy. The DEC.e-RTO™ Full-Electric Flameless RTO replaces the conventional fuel-fired auxiliary heat source with electric heating while retaining the regenerative heat-recovery principle. Under suitable VOC loading and stable operating conditions, oxidation heat and regenerative recovery can substantially reduce external heater duty; the complete energy balance must also include fans, dampers, controls and other auxiliary electrical loads.

Where full electrification is not yet the preferred operating strategy, the DEC.h-RTO™ Hybrid Dual-Energy RTO combines a flameless electric heating bank with a modulating gas burner around a shared regenerative oxidation system. Depending on the engineered operating envelope, the architecture can operate in 100% gas, 100% electric or controlled dual-energy modes. This can support staged electrification, energy-source flexibility, rapid cold startup and selected utility-resilience strategies.

The decision should not be based on heater efficiency alone. Electrical capacity, transformer and switchgear capacity, maximum demand, tariffs, gas availability, startup duty, VOC loading, regenerative effectiveness, pressure drop, operating hours and the site's Scope 1/Scope 2 strategy should be evaluated together. Electrification changes the energy source and direct combustion profile; it does not automatically reduce total energy demand.

For hybrid configurations, the DEC.HBT™ Heating Burner Train provides the engineered gas-heating interface, while DEC.HGB™ Hot Gas Bypass can provide a thermal-protection layer where concentration peaks approach defined limits. These technologies should be engineered together with the RTO's thermal balance, controls and safety systems.

Where excess heat is available and a suitable heat sink exists, DEC.ERS™ Energy Recovery Solutions can be evaluated for process air, thermal oil, hot water, steam or other technically suitable services.

12. Capacity, Process Flexibility and Future Production

Capacity assessment should include not only volumetric airflow but also the thermal and concentration envelope. A change in VOC concentration, calorific value or production mix can alter burner duty, electric heater duty, regenerative temperature and the need for thermal protection even where nominal airflow remains unchanged.

For high-volume, low-concentration streams, DEC.RBC™ Rotary Bed Concentrator may be considered upstream of an RTO to reduce the gas volume presented to the thermal oxidizer and increase VOC concentration. Where applicable, this can change the downstream thermal and electrical duty and should be included in the complete process balance.

An RTO that was correctly sized when installed may become constrained by production expansion, changed process capture, higher airflow, different VOC concentrations or a wider operating range.

A revamp may increase usable capacity through media optimization, airflow improvements, valve upgrades, control changes or selected chamber modifications. However, capacity claims should be demonstrated from the actual process envelope and not inferred from a component upgrade alone.

Published modernization examples show that retaining an existing RTO and adding chambers or other components can create a higher-capacity system. In one documented case, Dürr described relocating an existing three-tower RTO and adding two towers to create a five-tower system, increasing rated exhaust-air capacity from 75,000 to 110,000 m³/h.

13. Environmental Compliance and Permit Requirements

Revamping should be evaluated against the current environmental permit and the future operating requirements. A retrofit is not successful if it improves mechanical performance but leaves the installation unable to satisfy applicable emission limits, monitoring requirements or permit conditions.

• Identify current and pending emission limits.
• Review applicable BAT conclusions and environmental permit conditions.
• Assess whether process changes alter the regulated emission profile.
• Define required performance verification and monitoring.
• Check whether a modification, permit variation or other regulatory approval is required.
• Consider secondary emissions such as NOx, CO and greenhouse-gas emissions where relevant.

The assessment should distinguish between equipment capability and regulatory compliance. IED 2.0, national legislation and site permits can affect the modernization scope, but no universal replacement requirement should be assumed without installation-specific assessment.

14. Shutdown Planning and Project Execution

The main advantage of revamping an existing RTO can be reduced project duration compared with complete replacement, but this is not automatic. The scope should be engineered around the available shutdown window.

14.1 Long-Lead Activities

Order long-lead valves, ceramic media, refractory materials, PLC hardware, instruments and fabricated components before shutdown wherever the design is sufficiently frozen.

14.2 Parallel Work Packages

Where site safety and isolation rules permit, external fabrication, panel assembly, software development, media preparation and documentation can proceed in parallel with pre-shutdown engineering.

14.3 Commissioning and Performance Verification

The commissioning plan should include dry checks, loop checks, valve sequencing, burner and safety-system testing, temperature stabilization, airflow balancing, process introduction and performance verification against the agreed acceptance criteria.

15. Preliminary Feasibility for Third-Party RTOs

For RTOs manufactured by other vendors, DEC should receive sufficient basic documentation before defining a revamp strategy. Useful inputs include recent photographs and videos, technical data plate, model and serial number, GA and layout drawings, P&IDs, manuals, process data, airflow and VOC loading, maintenance history, ceramic-media information, valve and burner details, control architecture, known defects, utilities, lifting/access constraints and applicable site rules and policies.

The preliminary review should classify findings as documented, Customer-provided or requiring site verification. A desktop assessment should not be presented as confirmation of hidden internal condition.

16. Economic and Lifecycle Evaluation

The decision should compare the complete lifecycle implications of refurbishment, retrofit, rebuild and replacement rather than comparing only equipment purchase prices.

• Capital cost and installation cost.
• Shutdown and production-loss exposure.
• Temporary bypass or alternative abatement requirements.
• Energy and fuel consumption.
• Expected maintenance burden.
• Spare-parts availability and obsolescence.
• Environmental compliance and permitting costs.
• Remaining structural life.
• Future capacity requirements.
• Potential energy-recovery or electrification benefits.

Published refurbishment guidance emphasizes that the condition of the existing structure is a key determinant of whether refurbishment remains viable, while replacement introduces additional costs such as removal, disposal, new foundations and utility/duct modifications.

17. DEC Revamp and Modernization Framework

DEC can structure an existing-RTO modernization project through a staged engineering approach. The future-state architecture can include conventional fuel-fired operation, a full-electric DEC.e-RTO™, or a hybrid DEC.h-RTO™, depending on process duty, utility infrastructure, safety requirements and lifecycle objectives. A gas-fired modernization may incorporate the DEC.HBT™ Heating Burner Train, while concentration-peak protection may require evaluation of DEC.HGB™ Hot Gas Bypass.

DEC can structure an existing-RTO modernization project through a staged engineering approach:

1. Document review: collect equipment, process, maintenance and site information.
2. Condition assessment: establish mechanical, thermal, media, controls and airflow condition.
3. Performance baseline: quantify current airflow, pressure drop, energy and emissions performance.
4. Option engineering: define refurbishment, retrofit, rebuild and replacement alternatives.
5. Regulatory review: verify the future-state environmental and permit requirements.
6. Lifecycle evaluation: compare cost, downtime, energy, reliability and future capacity.
7. Execution planning: develop shutdown, procurement, site and commissioning plans.
8. Implementation: execute the selected scope and validate performance.

DEC provides dedicated DEC.RFT™ Retrofit and DEC.RFB™ Refurbish services for existing VOC abatement systems, including RTOs supplied by DEC or other vendors. The DEC service definition distinguishes retrofit as adding new technology or functionality, while refurbishment focuses on restoring an existing system to reliable operating condition.

Frequently Asked Questions

Engineering Basis and Technical Context

This engineering guide is based on established RTO engineering principles, DEC technical experience and the technical considerations applicable to the assessment, refurbishment, retrofit, rebuilding and modernization of regenerative thermal oxidizers. The recommendations should be applied to the specific equipment configuration, operating history, process conditions and applicable regulatory requirements.

DEC Related Technologies and Services

Relevant DEC resources for RTO modernization include:

• DEC.RFT™ Retrofit | DEC.RFB™ Refurbish
• DEC.XTO™ Thermal Oxidizers
• DEC.RTO™ Regenerative Thermal Oxidizers
• DEC.RTO_SMS™ Smart Modular System
• DEC.e-RTO™ Full-Electric RTO
• DEC.h-RTO™ Hybrid Dual-Energy RTO
• DEC.HBT™ Heating Burner Train
• DEC.HGB™ Hot Gas Bypass
• DEC.ERS™ Energy Recovery Solutions
• DEC.DMP™ Diagnostic Maintenance Program
• DEC.MRO™ Maintenance, Repair and Operations
• RTO-CCH Media Cleaning
• DEC.TSS™ Technical Support Services
• DEC.HDS™ Help Desk Services

Engineering Disclaimer

This guide is general engineering information and does not replace a site-specific inspection, process study, structural assessment, HAZOP or equivalent safety review, environmental permitting assessment, equipment manufacturer instructions, or advice from qualified local professionals. Actual retrofit, refurbishment and rebuilding scope must be determined from the specific RTO design, operating history, site conditions and applicable regulations.