Waste Gas Treatment for Lithium-ion Battery Anode Materials: Why Regenerative Thermal Oxidizer Is the Industry's Preferred Solution

With the rapid expansion of the global new energy industry, the production capacity of lithium-ion battery anode materials has kept rising. During the production of artificial graphite anodes, high-temperature processes such as calcination and granulation generate large volumes of complex industrial waste gas. This waste gas contains a wide range of toxic and Harmful Organic Compounds, alongside high proportions of flammable and explosive gases including hydrogen and methane, creating dual challenges for environmental compliance and production safety.

Conventional treatment technologies such as adsorption and absorption fail to simultaneously deliver high purification efficiency, reliable safety, and low operating costs. In contrast, Regenerative Thermal Oxidizers (RTOs), featuring thermal efficiency of over 95% and outstanding VOC removal performance, have gradually become the mainstream waste gas treatment solution for the lithium-ion battery anode sector.

1. Sources and Characteristics of Lithium-ion Battery Anode Waste Gas

Waste gas generated from anode production mainly originates from two core processes, which produce waste gas with vastly different compositions and properties. This means a one-size-fits-all treatment approach is not viable.

1.1 Waste Gas from Calcination Processes

Waste gas discharged during high-temperature anode calcination has an initial temperature as high as 400 °C under slight negative pressure. Nitrogen forms the primary carrier gas, with hydrogen accounting for more than 15% of the total volume. Additional components include methane, carbon monoxide, trace hydrocarbons such as ethane, ethylene, acetylene, and benzene. The defining traits of this waste gas are high temperature and high concentrations of combustible gases, resulting in significant explosion risks.

1.2 Tail Gas from Granulation Processes

Tail gas discharged from vertical granulators poses the greater treatment challenge among all anode production waste streams. Its core pollutants include asphalt fumes and non-methane total hydrocarbons, accompanied by methane, hydrogen, benzo[a]pyrene, and particulate matter. Key characteristics of this tail gas include high tar and particulate content, which readily adhere to and block ducts and treatment equipment. Benzo[a]pyrene, a potent carcinogen, is subject to extremely strict emission limit standards. Flammable gases are also present, introducing inherent safety hazards.

Overall, waste gas from lithium-ion battery anode production is simultaneously flammable and explosive, chemically complex, high in tar content, and laden with toxic and hazardous components. Treatment systems must address both environmental compliance and production safety in tandem.

2. Graded Treatment + Secondary Oxidation: Core Process Flow of the Complete System

To accommodate the distinct properties of the two waste gas streams, a combined process of Direct Thermal Oxidizer (TO) pre-treatment + rotary RTO deep purification can be adopted. Both waste gas streams are ultimately fed into a single RTO system to achieve compliant discharge, balancing treatment performance and operational cost-effectiveness.

2.1 Primary Incineration Process for Calcination Waste Gas

High-temperature, hydrogen-rich waste gas from calcination first undergoes primary safety incineration via a horizontal natural gas-fired TO furnace.

• Front-end safety control: Oxygen concentration in waste gas is maintained below 2% at all times to keep gas concentrations outside explosive ranges. Waste gas passes through a pair of cyclone oil separators(one operational, one standby) to remove particulate matter and viscous oily residues, preventing coking in downstream equipment.
• High-temperature oxidative decomposition: An induced draft fan delivers waste gas to the incinerator, where a stable temperature of 600–700 °C is maintained. Supplemental combustion air ensures full oxidation and breakdown of combustible components. Interlocks linked to furnace temperature automatically adjust natural gas supply and cooling air volume to sustain stable incineration conditions.
• Waste heat recovery and secondary treatment: Hot flue gas exiting the incinerator first passes through a gas-gas heat exchanger to recover waste heat, lowering flue gas temperature while cutting energy consumption. The cooled flue gas is then sent to the rotary RTO for secondary deep purification to guarantee fully compliant emissions.

Fig.2-1 A Photo of the Direct Thermal Oxidizer

2.2 Pre-treatment and RTO Purification Process for Granulation Waste Gas

Granulation tail gas with high tar loading undergoes multi-stage pre-treatment prior to final oxidation in the RTO.

• Cyclone oil removal pre-treatment: Waste gas flows into a pair of cyclone oil removers (one operational, one standby). Centrifugal force eliminates most tar and particulate matter, protecting the RTO's regenerative ceramic media from clogging.
• Air dilution and spray dehumidification: Waste gas enters a static air mixer, where fresh air dilutes gas concentrations to below 25% of the Lower Explosive Limit (LEL) to eliminate explosion risks. Built-in water spray inside the mixer further removes dust and raises waste gas humidity to prevent static electricity generation. After dehumidification at the mixer outlet, the mixed gas is conveyed to the RTO by a main fan.
• Deep oxidation via rotary RTO: The rotary RTO with a design treatment air volume of 10,000 m³/h serves as the core of the entire solution. Guided by a rotary distribution valve, waste gas first flows through regenerative chambers to absorb heat stored in ceramic media, preheating to over 760 °C before entering the combustion chamber. At a sustained temperature of 850 °C, gas maintains a residence time of no less than 1.2 seconds, enabling complete oxidative decomposition of VOCs, asphalt fumes, benzo[a]pyrene and other pollutants. Purified clean gas releases heat as it passes through the opposite regenerative chamber to cool down, before being vented through an exhaust stack. The RTO delivers thermal efficiency of ≥95%, drastically reducing natural gas operating consumption.

Fig.2-2 A Photo of the Rotary Regenerative Thermal Oxidizer

3. Multi-layer Emergency Safeguards to Reinforce Safety Barriers

Given the high concentrations of combustible components such as hydrogen and methane in the waste gas, safety design is the top priority of the integrated solution. Comprehensive emergency safeguards cover all operational scenarios, including normal running, fault switching, and maintenance.

1. Concentration early warning and emergency venting. LEL and hydrogen content detectors are installed at key monitoring points to track real-time waste gas concentrations. When concentrations exceed safety thresholds or system abnormalities occur, automatic shut-off valves immediately isolate the intake duct while emergency vent valves open. Waste gas passes through an activated carbon adsorption box for purification before emergency discharge, preventing high-concentration gas from entering the furnace and triggering safety incidents.
2. Redundant critical equipment and safe switching. Prone-to-clog and high-wear equipment including cyclone separators and circulation pumps adopt a one-operate-one-standby configuration. Seamless switching to standby units is possible during single-unit faults or cleaning without disrupting main production lines. Before equipment switching, internal ducts are purged with nitrogen to fully displace residual combustible waste gas, safeguarding maintenance personnel.
3. Furnace safety and interlock protection. Both the TO incinerator and RTO furnace bodies are fitted with explosion relief panels to rapidly release pressure in the event of in-furnace flash fires and prevent permanent equipment damage. Furnace temperature and pressure signals are interlocked with gas supply valves and fans; over-temperature or over-pressure conditions trigger automatic operating parameter adjustments, with an emergency furnace shutdown activated under extreme conditions.
4. Full-process explosion protection and static elimination. All electrical components and fan motors in waste gas contact zones feature explosion-proof construction compliant with ATEX Zone 2 standards. Additionally, an independent nitrogen purging system is deployed to fully displace combustible gas accumulations in ductwork, separators and furnace chambers during furnace startup, shutdown and equipment maintenance.

4. Conclusion

Waste gas treatment for lithium-ion battery anode manufacturing essentially requires striking an optimal balance between environmental compliance and production safety. This integrated solution of graded pre-treatment paired with RTO deep oxidation specifically addresses core industry pain points including tar clogging and high explosion risks from concentrated combustible gas streams. The regenerative thermal oxidation technology delivers ultra-high thermal efficiency to lower long-term operating costs, while multi-tiered emergency safety designs fully satisfy stringent compliance standards such as EU CE and ATEX directives. As environmental and safety regulations for the lithium battery industry continue to tighten, this treatment framework centered on safety prioritization, balanced operational efficiency, and full regulatory compliance will become the preferred choice for an increasing number of anode manufacturers.