Case Study | A New Energy-Saving Approach to VOCs Control in the Coatings Industry! RTO Waste Heat Recovery Turns Waste into Valuable Resources, Reducing Energy Consumption and Operating Costs.
In the VOCs treatment process of the coatings industry, RTOs (Regenerative Thermal Oxidizers) are typically used as the core treatment equipment. Leveraging heat-storage technology, these devices inherently possess energy-saving advantages. Moreover, through systematic and optimized design, there remains significant potential for further cascaded utilization of the flue gas waste heat.
Recently, a globally renowned coatings company implemented an RTO waste heat recovery retrofit, converting exhaust gas waste heat into hot water for production. This move not only aligns with policies aimed at energy conservation and consumption reduction but also helps lower operational costs, making it a benchmark model for green transformation in the industry!
Project Background: The “Waste Pain Point” of Waste Heat from RTO Exhaust Gases
The company previously operated a VOCs treatment system consisting of a “zeolite rotor + RTO” unit, which was used to treat organic exhaust gases generated during the workshop’s production process. The RTO is designed for a maximum exhaust air volume of 10,000 m³/h, with exhaust gas temperatures reaching up to 150℃ (fluctuating depending on the season and the concentration of the exhaust gases). This high-temperature tail gas is discharged directly, not only wasting thermal energy but also failing to meet the company’s development goals of energy conservation and reduced consumption.
Core project requirement: Recover the waste heat from RTO exhaust gases to produce 70℃ hot water, thereby replacing part of the conventional heating equipment. At the same time, ensure that the stability of the existing VOCs treatment system is not affected and that safety and intelligent control requirements are met.
Core difficulty: The “precondition threshold” for waste heat recovery
Not all RTOs are suitable for waste heat recovery; two key conditions must be met, otherwise the significance of recovery will be greatly diminished.
1. The exhaust gas flow rate and concentration must remain stable.
A stable exhaust gas flow rate and concentration are the core elements for maintaining a constant exhaust gas temperature in the RTO system. They can provide a continuous and stable heat source for the waste heat recovery unit, thereby meeting the production workshop’s demand for uninterrupted utilization of waste heat.
2. The RTO system must maintain a self-thermal equilibrium state.
If the VOC concentration in the exhaust gas is relatively low, the RTO needs to maintain the oxidation reaction temperature by supplementing with large amounts of auxiliary fuels such as natural gas. Under these operating conditions, priority should be given to optimizing the RTO’s operational parameters to reduce the system’s own energy consumption, while recovering waste heat from the exhaust gas should be considered a secondary factor.
Based on the actual operating conditions of the enterprise, the RTO system operates in a stable state, and its exhaust gas flow rate and concentration parameters both meet the requirements for self-thermal balance, providing the necessary foundation for efficient waste heat recovery.
Megaunity Solution: Turning waste heat into hot water—energy-efficient and reliable.
Addressing enterprise needs, Megaunity has designed a waste heat recovery system—featuring “RTO exhaust gas + gas-to-water heat exchanger”—with “safety and stability, efficient recovery, and intelligent control” at its core, thereby enabling the resourceful utilization of thermal energy.
1. Core principle: Waste gas waste heat → Production of hot water
After combustion in the RTO, the exhaust gas is passed through a gas-to-water heat exchanger to exchange heat with cold water, raising the water temperature to 70℃ before being supplied to the workshop for production. Theoretically, under maximum operating conditions, 5 tons per hour of 20℃ cold water can be heated to 70℃; in practice, the actual hot water output ranges from 1 to 5 tons per hour (dynamically adjusted according to operating conditions).
2. Dual-mode operation: Flexibly adapts to different operating conditions
Parallel Mode: The waste heat recovery system is connected in parallel with the original hot water heater. Waste heat is prioritized for water production, while the original heater serves as a backup.
Warm-up mode: If the RTO exhaust gas temperature is low (e.g., in winter) and the water temperature after heat exchange fails to meet the standard, the system will automatically switch the heated water from the heat exchanger back to the original heater for supplemental heating, ensuring a stable supply of hot water.
3. Key equipment: Balancing safety and durability
Core equipment: air-water heat exchanger (304 material), explosion-proof variable-frequency fan (temperature resistance up to 200℃, explosion-proof rating ExDIIBT4), and one working and one standby 304-material water pump (corrosion-resistant).
Safety Protection: Implement interlocks for high pressure and high temperature that are linked to the RTO. High-temperature components are equipped with thermal insulation protection to prevent burns.
4. Smart Control: Fully automated, making operations and maintenance more worry-free.
Data Interconnection: The new system is now connected to the original RTO PLC, enabling real-time monitoring of parameters such as temperature, flow rate, and pressure, with data storage for traceability.
Remote Management: Supports cloud-platform monitoring via PC and mobile devices; alerts for exceeding standards or temperatures are directly sent to relevant personnel, and faults can be remotely diagnosed.
One-click operation: In automatic mode, simply press the start button to complete the interlocked control. In manual mode, individual components can be operated separately. In case of a fault, the system provides built-in solutions for troubleshooting.
Implementation Results: Double Benefits—Energy Savings and Cost Reduction
After the project is put into operation, it will achieve dual benefits—environmental protection and energy conservation.
Heat Recovery: The RTO exhaust gas waste heat utilization rate exceeds 70%, producing 1–5 tons/hour of hot water, which meets most of the workshop’s hot water demand.
Cost optimization: By replacing traditional electric/gas heating, annual energy consumption costs are reduced by tens of thousands. The original heater is now used only as a backup, thereby reducing equipment wear and tear.
Stable and reliable: Seamlessly integrated with the original VOCs treatment system, without affecting compliance with emission standards for waste gases.
Compliance Bonus: In response to the nation’s “Dual Carbon” policy, this has become a key highlight of corporate green production.
After-sales guarantee: Quick response, no worries whatsoever.
As the general contractor for the project, Megaunity provides full-cycle service support:
Rapid Response: The local operations and maintenance team will arrive on-site within 2 hours, and 24-hour online technical support is available.
Regular Maintenance: Provide equipment diagnostics quarterly and develop energy-saving optimization plans.
Lifetime Service: We continue to provide lifetime process improvements even after the warranty period, ensuring compatibility with environmental standards and adapting to changes in production.
In the coatings industry, VOCs treatment should not only meet regulatory standards but also achieve energy efficiency! Megaunity offers customized waste heat recovery solutions that transform RTO exhaust gases from “waste heat” into “resources,” helping companies reduce operational costs while supporting their green transformation.
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