A Successful VOC Gas and Liquid Waste Treatment System for a Propylene Oxide Plant in China

A Single Solution for Both VOC Gases and Waste Liquid for Propylene Production

THE CHALLENGE

A leading petrochemical company in China constructed a new propylene oxide (PO) production facility. The process generates substantial volumes of waste gas and liquid containing a complex pollutant mix: VOCs including methanol, ethanol, propylene oxide and acetone, along with inorganic compounds such as nitrogen, ethane, propylene, propane, hydrogen peroxide, methyl ether, methane, and hydrogen.

As environmental regulations in China continue to tighten, local authorities required a dedicated treatment system meeting the national standard GB31571-2015 for petrochemical industry and applicable provincial standards before the plant could commence operation.

TAKING ACTION

To address this critical need, the petrochemical company turned to again Anguil. They had prior experience with Anguil equipment having two treatment systems installed for other applications in the region which demonstrated stable long-term performance. Based on this track record, the client commissioned Anguil to design, supply, and commission the treatment system for the new PO plant.

THE SOLUTION

After conducting a comprehensive analysis of the waste stream composition, emission requirements, and operational conditions, Anguil engineers designed a tailored solution for the unique process: an integrated system combining a Thermal Oxidizer (TO), waste heat boiler, Selective Catalytic Reduction (SCR) denitrification unit, economizer, and activated carbon adsorption backup system. This combination was chosen for its ability to address the complex pollutant mix, meet strict emission limits, and deliver economic and environmental benefits.

Waste Gas and Liquid Profile

The streams to be treated originate from multiple process points across the PO plant, including reactors, separation columns, and the intermediate tank farm. Composition, flow rate, and thermal content differ significantly across these sources. Several streams carry high concentrations of combustible organics with wide flammability ranges; others are inert-heavy or dilute. A portion of the pollutant load is in liquid phase, requiring atomized injection rather than standard gaseous feed. This variability demanded a purpose-designed inlet and combustion configuration to ensure complete treatment across all operating scenarios.

Process Flow: From Contamination to Compliant Emission Exhaust

• High-Temperature Oxidation: Combustible pollutants in the waste gas and liquid are injected into the TO via specialized nozzles, atomized with steam for optimal dispersion. Operating at a high temperature of 1,100 ℃, the TO oxidizes the contaminants in an oxygen-rich environment, converting them into water and carbon dioxide.
• Waste Heat Recovery: The high-temperature purified flue gas (carrying substantial thermal energy) is directed to a waste heat boiler that recovers the thermal to produce 30 t/h of superheated steam at 2.4 MPa. The client can reuse the steam in the PO plant’s production processes.
• Denitrification (SCR): High-temperature combustion in the TO produces thermal NOx as a byproduct. To bring NOx within regulatory limits, flue gas is cooled to approximately 320 ℃ and is routed to an SCR unit, where NOx is reduced to nitrogen and water through catalytic reactions, ensuring compliance with NOx emission standards.
• Secondary Heat Recovery: To maximize energy efficiency, an economizer (equipped with a deaerator) is installed at the SCR outlet. This device preheats boiler feedwater by using the remaining thermal from the flue gas, lowering the final exhaust temperature to 160 ℃, improving overall thermal efficiency and reducing stack heat losses.
• Final Emission: The treated flue gas is drawn through a negative-pressure fan and discharged into the atmosphere via a stack, fully meeting the required environmental standards.

Key Advantages of the Integrated System

The solution was designed to address not just compliance, but also the client’s operational and economic needs—offering five core advantages:

High Destruction Efficiency with Energy Saving

The TO is the heart of the system, delivering a pollutant destruction efficiency above 99.9% while optimizing energy use:

• Complete Oxidation: The TO’s design—including strategically selected and positioned burners, plus internal baffles—ensures thorough mixing of waste gas/liquid and combustion air. The baffles extend the flue gas residence time and promote turbulence, guaranteeing the complex pollutants are fully oxidized.
• Energy Recovery: The waste heat boiler transforms waste thermal energy into usable steam, creating significant economic value. The steam output is matched to the PO plant’s process requirements and fed directly into the plant’s utility distribution system, displacing equivalent natural gas-fired steam generation. At current energy prices, this represents over RMB 50 million in annual economic benefits for the client—turning a compliance cost into a revenue-generating asset.

Smart Burners: To adapt to the plant’s varying operational conditions, combined burners were utilized. This design reduces the total number of burners required and allows real-time adjustment of fuel output to match varying waste gas volumes, minimizing supplemental fuel consumption while maintaining stable combustion temperature.

Superior Safety Assurance

Safety is paramount in petrochemical operations, and the system was engineered to meet the highest global standards:

• Compliance with International Standards: The TO is designed in accordance with the U.S. NFPA 86 standard, a globally recognized benchmark for thermal oxidizer safety.
• Hazard Analysis & Simulation: A Hazard and Operability (HAZOP) analysis is conducted to identify and mitigate potential risks. Advanced simulation tools were also used during the design phase to optimize system parameters, ensuring safe operation under all expected conditions.

Explosion‑Proof and Safety Instrumentation Provisions: All field instruments are specified to explosion-proof standards. Flame arrestors, combustible gas detectors, and emergency shutoff valves are installed at critical inlet and outlet points.

Low Failure Rate for Reliable Long-Term Operation

To minimize downtime and maintenance costs, the reliability is prioritized in component selection and system design:

• High-Quality Components: Electrical and instrumentation parts are sourced from internationally recognized, industry-proven brands—ensuring durability and performance.

Optimized Controls: Rational control system design reduce the risk of component failure, ensuring the system operates stably with minimal interruptions.

Simple and Convenient Operation

The entire system is fully integrated with a Distributed Control System (DCS) and Safety Instrumented System (SIS), enabling full automation. No dedicated on-site operators are required for routine operation—only regular inspections are needed. Both systems allow remote monitoring and control, simplifying management and reducing labor costs.

Emergency Backup for Uninterrupted Compliance

An activated carbon adsorption system is dedicated to the intermediate tank farm’s waste gas. Under normal operation, this stream is processed through the TO. When the TO is offline for planned or unplanned maintenance, the tank farm exhaust is automatically diverted to the adsorption unit, where VOCs are captured before discharge via stack. This maintains continuous compliance without requiring additional operator intervention.

THE RESULTS

Since commissioning, the system has operated stably with no significant unplanned downtime. Destruction efficiency is maintained at 99.99%, and emissions of NMHC, acetone, phenols, methanol, and NOx consistently remain below the limits defined in GB31571-2015 and DB32/315-2016. The project met the environmental compliance requirements for the new production unit and has supported uninterrupted operation since startup.

The system’s consistent performance reinforced the client’s confidence, and they subsequently selected Anguil to design and supply waste gas treatment equipment for another new production facility. That project equally met all design requirements and performance targets upon commissioning. The repeat engagement reflects the client’s sustained satisfaction with Anguil’s technical capability and long-term service support.

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Waste Gas Treatment for Polyamide Film Production in China

THE CHALLENGE

Polyamide (PI) film is a high-performance material renowned for its exceptional insulation properties, making it indispensable in electronics, aerospace, and automotive industries. A Chinese film producer recently planned to build a new PI film production line to meet growing market demand. However, the production process—specifically the imidization process adopted for the new line—posed a significant environmental challenge: it would generate large volumes of waste gas during film formation and spreading stages.

The waste gas, with a flow rate of 31,000 SCFM (50,000 Nm³/h), contained key pollutants including N,N-Dimethylformamide (DMF), isoquinoline, acetic anhydride, and acetic acid. A critical concern was NOₓ emissions: since DMF and isoquinoline are nitrogen-containing compounds, their oxidation during treatment could produce NOₓ. To comply with national and local environmental standards, the producer required a waste gas treatment system that not only removes Volatile Organic Compounds (VOCs) but also strictly controls NOₓ levels, reducing the facility’s carbon footprint.

THE SOLUTION

After a comprehensive evaluation of technical feasibility, energy efficiency, and compliance potential, the producer partnered with Anguil in Asia to design and construct a tailored waste gas treatment system. The core design integrated four key functions: VOCs abatement, waste heat recovery, denitrification, and real-time monitoring. This ensured the system met both emission standards and the producer’s operational cost goals.

Full Process Flow Overview

The waste gas treatment process follows a sequential, high-efficiency design to maximize pollutant removal and energy reuse:

Waste Gas Inlet: Raw waste gas is first directed to an LEL (Lower Explosive Limit) detector to monitor combustible gas concentration, ensuring it stays below safe thresholds to prevent combustion risks.

Thermal Oxidizer (TO): The pre-screened gas enters the TO, where VOCs (e.g., DMF and acetic anhydride) are oxidized at high temperatures into CO₂ and H₂O, along with a small amount of NOₓ.

Heat Exchangers:

Heat Exchanger #1: Captures heat from the TO’s high-temperature exhaust to preheat combustion air to over 392°F (200°C), reducing fuel consumption.
Heat Exchanger #2: Further recovers waste heat to preheat incoming waste gas from approximately 302°F (150°C) to over 932°F (500°C), minimizing the TO’s energy demand.

Boiler: The remaining high-temperature exhaust, after heat exchange, is routed to a boiler where it generates saturated steam for the PI film production line’s heating processes.

SCR System: After steam generation, the exhaust passes through a Selective Catalytic Reduction (SCR) system equipped with high-performance catalysts that convert NOₓ into N₂ and H₂O, ensuring regulatory compliance.

Economizer: The cooled exhaust then flows through an economizer to preheat boiler feedwater, maximizing final heat recovery.

Induced Draft Fan & Stack: Downstream is an induced draft fan pushes the treated exhaust through the stack, which is equipped with an explosion-proof Continuous Emissions Monitoring System (CEMS) for real-time emissions monitoring.

Key Equipment Advantages

Each component of the system is optimized for efficiency, compliance, and reliability:

Thermal Oxidizer (TO): As the core of VOCs abatement, it features two critical designs:

• Choke Ring Structure: Installed inside the TO, this structure enhances gas turbulence, extends the gas residence time, and ensures uniform mixing—boosting VOCs removal efficiency to over 99.9%.
• Low-Nitrogen Burner: Reduces the formation of thermal NOₓ (NOₓ generated from high-temperature air oxidation) by controlling combustion temperature and oxygen distribution, addressing NOₓ risks at the source.

Waste Heat Recovery Boiler: Converts waste heat from the TO’s exhaust into saturated steam of 6.5 tons/hour, 1.0MPaG which is reused in the PI film production line. This not only replaces the need for a separate steam boiler but also cuts the producer’s annual energy costs significantly.

SCR System: Uses high-performance dedicated catalysts to remove NOₓ. It is paired with an online NOₓ analyzer that monitors exhaust NOₓ concentration in real time and automatically adjusts the reducing agent (e.g., ammonia) injection rate—ensuring stable NOₓ control even with fluctuating waste gas composition.

LEL Detector: Installed at the waste gas inlet, it provides 24/7 monitoring of combustible gas levels. If concentrations approach the explosive limit, the system triggers an alarm and adjusts gas flow, preventing safety hazards.

Explosion-Proof CEMS: Mounted on the stack, the Continuous Emission Monitoring System (CEMS) tracks key pollutants (NOₓ, VOCs, Non-Methane Hydrocarbons/NMHCs) and transmits real-time data to local environmental monitoring authorities. This ensures full transparency and compliance with regulatory reporting requirements.

THE RESULTS

The waste gas treatment system was completed and put into operation. After a one-month trial run and official testing, the system achieved outstanding performance:

• VOCs Removal: VOCs removal efficiency reached 99.9%, far exceeding the minimum requirement of 95%.
• NMHC Compliance: The treated exhaust’s NMHC concentration was measured at 10 mg/Nm³, well below the local standard limit of 30 mg/Nm³.
• NOₓ Control: NOₓ concentration in the stack exhaust was 40 mg/Nm³, significantly lower than the national standard limit of 100 mg/Nm³.

Beyond compliance, the system delivered substantial economic benefits. The boiler’s saturated steam supply stably, reduce the producer’s natural gas consumption and cutting annual operating costs. The heat exchangers’ energy recovery reduced the TO’s fuel consumption, further lowering energy expenses.

By combining thermal oxidation, waste heat recovery, and SCR denitrification, Anguil Asia’s solution not only helped the producer meet strict emission standards but also turned waste gas into a valuable energy resource. As environmental regulations continue to tighten, such “treatment + energy reuse” solutions will become increasingly critical for balancing industrial development and ecological protection.

Scaling Sustainability in China’s Chemical Sector

THE CHALLENGE

In the highly competitive field of chemical engineering, environmental protection and sustainable development have become the key indicators for measuring the success of projects. A world – leading chemical company, with a vision for the future and a commitment to environmental stewardship, launched a major integrated Refining and Chemical Project in China. As an essential supporting utility of this grand project, the waste water treatment plant faced a significant challenge: finding a reliable solution provider with extensive international experience in treating the complex waste gas sources generated by the plant.​

The waste gas emitted from the plant presented a complex and challenging situation. It originated from two distinct sources. One source was the waste water exhaust, which had a relatively low concentration of pollutants but a high flow rate of 20,000 Nm³/h. The other source was the process exhaust from the client’s production line, characterized by high – concentration pollutants yet a low flow rate of 100 Nm³/h. The main VOC pollutants in these waste gases were a mixture of harmful substances, including Formaldehyde, Benzene, Toluene, Xylene, H₂S, NH₃, and others.​

The client, being a top-class global company, had extremely high and stringent requirements across all aspects of the project. From the strict adherence to international standards and codes, meticulous control over fabrication processes, careful selection of coupled materials, to on – site management and quality control, every detail was closely scrutinized. The documentation work was also a massive task, with project progress and related documents needing to be updated on a weekly basis. This comprehensive set of demands made the selection of a suitable solution provider a difficult decision.​

After a rigorous process of comparing various potential partners, the client finally selected Anguil Asia. Headquartered in U.S. for over 40 years, Anguil Asia has the advanced and reliable technologies in the VOC abatement industry, a high reputation and world-class services.

Its strong international background and the impressive track record of successful installations in similar applications aligns with the client’s expectation for a supplier. The client believed that Anguil Asia had the expertise and capabilities to meet their high – level requirements and solve the complex waste gas treatment problem.​

THE SOLUTION

To address the unique characteristics of the waste gas and meet the client’s strict requirements, Anguil Asia proposed a comprehensive and innovative solution: an RTO (Regenerative Thermal Oxidizer) system incorporated with scrubbers.

RTO, or Regenerative Thermal Oxidizer, is a highly efficient waste gas treatment technology widely adopted in various industrial sectors. It consists of a combustion chamber and two or more regenerative chambers filled with ceramic media. Within the combustion chamber, waste gas with VOC pollutants is heated to 750 – 950°C, decomposing VOCs into CO₂ and water, and simultaneously releasing heat energy. The Ceramic materials in the regenerative chambers can alternately absorb a large amount of heat from the hot outgoing gas and then release this heat to pre – heat the incoming cold exhaust gas in the subsequent process, improving the thermal efficiency of the RTO.

In order to maintain optimum heat recovery efficiency of the regenerative chamber, the waste gas flow direction is switched at regular intervals by the automatic diverter valves on demand from the DCS control system. This periodic flow direction shift provides a uniform temperature distribution throughout the entire oxidizer.

Specifically, Anguil Asia recommended a 3 – chamber RTO system, which offers higher destruction efficiency compared to a 2-chamber system, and it was coupled with one set of pre – scrubber, a quench device, and one set of Alkali Scrubber. Additionally, a set of emergency Activated Carbon system was included to ensure maximum safety and reliability.

Fully understanding the client’s high-standard demands and committed to close cooperation in all aspects, Anguil Asia implemented strict quality control measures at every production stage in manufacturing, ensuring that each component used in the waste gas treatment system met the required standards. The materials selected were of excellent quality, sourced from reliable suppliers known for their durability and performance in industrial applications. Regarding quality management, the company had a comprehensive inspection process to eliminate any potential defects. On – site management was also a key focus. The installation and commissioning team on – site worked in tandem with a well – organized overall team, ensuring smooth operations, efficient resource allocation, and strict compliance with safety regulations.

In terms of documentation, a dedicated team is established to handle the massive amount of paperwork. They ensured that all project progress reports and related documents were accurately updated and submitted on time every week, maintaining a high level of transparency and communication with the client.​

Safety was a top priority in this project. The RTO is incorporated with a hot gas bypass system. When the pollutants concentration was high, part of the gases could be bypassed from the RTO combustion chamber, effectively preventing potential over – temperature or explosion risks and ensuring the safety of the RTO system. Additionally, the emergency Activated Carbon system was crucial. In case the RTO was out of work or malfunctioned, the waste gas could be emergently diverted through this system to the stack, eliminating the risk of explosion caused by the accumulation and expansion of waste gas within the oxidizer.​

Given that the waste gas contained corrosive substances, Anguil Asia took multiple precautions. Before the waste gas entered the RTO, a pre – scrubber was installed to effectively remove acid substances such as H₂S. After the RTO process, to eliminate the SO₂ generated during combustion, an Alkali Scrubber, along with a quench, was incorporated. Moreover, considering the high salt fog environment near the sea where the RTO system was located, which posed another source of corrosion, Anguil Asia made strategic material choices and treatments. For instance, the pipeline and bolts were made of PTFE (Polytetrafluoroethylene), a highly corrosion – resistant material. In high – temperature areas, ceramic fasteners were used to ensure stability and durability. The paint film for the oxidizer was applied with a much thicker layer than normal to enhance its anti – corrosion properties.​

To meet the high requirements for the oxidizer’s strength and sealing performance, Anguil Asia deviated from the normal practice. When welding the oxidizer reinforce rib, instead of using intermittent welding, a complete welding process was adopted. This meticulous approach significantly enhanced the structural integrity and sealing of the oxidizer, ensuring its long – term stable operation under harsh conditions.​

THE RESULT

With the implementation of a well-designed and carefully executed solution, the RTO system is expected to achieve outstanding results. It is projected to fully meet the client’s strict requirements, ensuring VOC emissions adhere to both national and industry standards. This success showcases Anguil Asia’s technical and project management skills, while also promoting the client’s sustainable development.

Waste Gas Treatment for a Carbon Fiber Recycler

THE CHALLENGE

A carbon fiber recycling company in China plans to launch a new project aimed at recycling waste high-performance carbon fiber and producing carbon fiber composite products.  The recycled carbon fiber is utilized to produce the automotive components.

All processes, from storage and crushing of waste carbon fibers to microwave pyrolysis product collection, must strictly adhere to the VOC emission control standards. The waste tar and other by-products generated are classified as hazardous wastes, and their storage, transportation and disposal must comply with relevant national hazardous waste regulations.

After a detailed assessment of various suppliers, the factory chose Anguil Environmental Asia (Shanghai) Ltd. to solve the problem of waste gas emissions. Anguil Asia has developed and refined their waste gas abatement technology over decades, specially applying in carbon fiber industry. They have successfully installed numbers of effective equipment in this field, earning a reputation for their reliable quality and service.

THE SOLUTION

Before equipment selection, Anguil Asia conducted an energy analysis of the on-site equipment. Based on the required removal efficiency and the exhaust gas parameters, this analysis helped to choose the best treatment technology.

For this project, the main source of waste gas is the pyrolysis stage of the recycled carbon fiber resin. The main VOC pollutants are benzene series compounds, along with carbon fiber particulate dust and tar. Considering the high VOC concentration in the waste gas and the presence of tar derived from microwave pyrolysis processing, Anguil Asia selected a TO (Thermal Oxidizer) equipped with heat exchangers, bag filter and SCR (Selective Catalytic Reduction) system.

The waste gas first enters a thermal oxidizer (TO), where it is decomposed into H₂O and CO₂ at high temperatures and released a large amount of heat. The gas then flows to heat exchangers at the TO outlet, which recover the excess heat for cyclic energy utilization. Next, the gas passes through a dust collector installed downstream of the heat exchangers to remove silicon powder from the carbon fiber precursor. Finally, it goes through a SCR to eliminate nitrogen oxides generated during combustion in the TO, the treated gas is then be clean and discharged in to the atmosphere.

The whole system has the following features to ensure that the system is stable, reliable and efficient:

1. High-Efficiency Thermal Oxidizer (TO) Design for High-Concentration Exhaust Gas: Anguil recommended a TO with an airflow rate of 600m ³ h to effectively treat high-concentration exhaust gas. The cylindrical oxidizer body has an inner cavity insulated with ceramic fiber cotton to maximize the heat efficiency and ensure safe operation. To achieve complete waste gas combustion, the selection and layout of the burners are specially considered; for variable operating conditions, the burner can adjust the fuel output in real-time according to the gas volume for energy savings and emission reduction. The oxidizer’s interior is also specially designed for easy cleaning in case of tar adhesion, ensuring long-term safe operation. Furthermore, Anguil specially designs the pipeline to prevent blockages caused by carbon fiber particles, tar, and other substances in the exhaust gas.

2. Waste Heat Recovery and Temperature Control System: To effectively utilize the waste heat from the oxidizer, a gas-gas heat exchanger is employed to preheat the fresh air, which is then mixed with waste gas in a mixing box and introduced into TO unit.  Additionally, a gas-water heat exchanger is installed to cool the gas with cooling water before it is directed to the dust collector and SCR system for further processing.

3. Online Soot Blowing for Heat Exchanger: Benefiting from Anguil Asia’s mature design and extensive experience in carbon fiber industry, the heat exchanger is equipped with soot blowers for online cleaning, and ensuring continuous production.

4. Integrated Dust Removal Unit and Flexible Cleaning Control: The dust removal unit integrates three key processes: baghouse filtration, ash transfer, and packaging. The system features dual-mode “Remote/Manual” cleaning control. In automatic mode, a pulse controller manages timed cleaning cycles. The manual mode is primarily used for system startup, shutdown, and maintenance.

5. IDLE Mode for Flexible Production Scheduling Adaptation: To meet the customer’s flexible production schedule, an IDLE mode was integrated into the PLC program. When the production line is down, this mode maintains the oxidizer at a lower temperature, significantly shorten the reheating time when resume operation.

6. Fully Automatic PLC Control System: The system is equipped with a fully automatic control system centered on a PLC, which significantly reduces labor costs. The system features integrated hardware and software interlocks, ensuring precise and rapid control to effectively guarantee operational safety.

THE RESULT

Utilizing natural gas as an auxiliary fuel, this system achieves excellent performance in treating high-concentration waste gas, with a destruction efficiency of up to 99.99%.  After the abatement, the VOC concentration complies with both national and local VOC emission control standards. The system has successfully met all design objectives, demonstrating its outstanding effectiveness in VOC abatement.

Multi-Staged Combustion or Selective Catalytic Reduction?

The Challenge

Many industrial furnaces operate in oxygen depleted conditions, emitting high levels of ammonia, NOx, and other nitrogen-bearing compounds. This presents a significant challenge for manufacturers striving to meet air quality regulations and limit carbon output.

Emission streams that contain nitrogen bearing hazardous air pollutants (HAPs) cannot be thermally treated in a traditional oxidizer system without forming additional NOx, making adherence to an air permit difficult or impossible. In such cases, a secondary abatement device, downstream of the thermal oxidizer is required for additional NOx reduction.

Historically, the industry has relied on Selective Catalytic Reduction (SCR) systems to achieve this. The add-on technology injects ammonia or urea into the process stream before passing it through a specialized catalyst that converts the NOx into nitrogen gas (N2) and water vapor. However, this approach comes with significant operational burdens:

• The need for ammonia or urea storage, pumps, and customized control systems to maintain injection rates.
• High operating costs due to chemical consumption, catalyst maintenance, and periodic replacement.
• Fresh air must be added to dilute the inert process streams to safe levels, increasing the treatment volume and leading to condensation issues.
• Additional winterization equipment to prevent freezing in cold water climates.

It essentially requires a small chemical operation to remove the NOx and the staff to support it.

The Solution

Over the past four decades, Anguil has provided thousands of thermal and catalytic oxidizers around the world, many of which incorporated SCR technology. Recognizing the inefficiencies, engineers at Anguil came up with a better solution. The objective was to maintain very high levels of HAP removal, eliminate the catalyst and associated maintenance, prevent the need to dilute the stream making it safer to operate, and eliminate the use of add-in chemicals.

This solution was a Multi-Staged Direct Fired Thermal Oxidizer (MS-DFTO) – a groundbreaking approach that compartmentalizes the oxidation process across multiple temperature-controlled stages with varying oxygen levels, to dramatically reduce the formation of greenhouse gases.

In the MS-DFTO the nitrogen bearing HAPs are introduced into the first stage of the thermal oxidizer, the reducing zone, that operates at elevated temperatures, but without oxygen. This serves to disassociate the HAPs while not forming NOx from any nitrogen bearing compounds in the absence of oxygen. Special operational sequences ensure starved oxygen is maintained in the first stage. The high temperature, oxygen depleted gas leaving this first stage is then rapidly cooled in a second stage to near the oxidation temperature. At this cooler temperature, the gases are reintroduced to air in the third chamber where the complete combustion of compounds occurs. Design considerations are made to ensure that the temperature after oxidation does not escalate to where thermal NOx could be formed, generally above 1,800°F (982°C).

Specialized refractory insulation and highly automated controls for the various stages of the Anguil MS-DFTO minimize auxiliary natural gas consumption. Properly staging the operating conditions and temperature profile throughout the MS-DFTO will result in destruction rates of the hazardous compounds and volatile organic compounds with minimal NOx formation in a single system.

In select applications, a fourth stage of the MS-DFTO has been added to provide Selective Non-Catalytic Reduction (SNCR) as a safety factor to ensure even fewer NOx emissions. Experience has shown that these fourth SNCR stages are not necessary and rarely used even when supplied as the NOx emissions have always met permit requirements without the need for this polisher.

The Result

This staged combustor from Anguil is reshaping how industries approach greenhouse gas abatement from process furnaces. On this application, the Anguil MS-DFTO was treating 5,000 SCFM (8,025 Nm3/hr) of process air in a single abatement device with well over 99% HAP destruction and NOX emissions that were a small fraction of the allowable permit value. The equipment does not require chemical injections or active catalyst maintenance, meaning a heavily reduced operational cost relative to an SCR. Inert process streams can remain inert, meaning a safer system can be supplied that does not require upstream dilution. Treating a fraction of the air also means the upstream process ducting can be smaller, saving cost all around.

Industrial facilities continue implementing Environmental, Social, and Governance (ESG) strategies to comply with regulations, improve sustainability, and meet stakeholder expectations. This ESG initiative met those objectives and reduced equipment cost, footprint, and maintenance costs, while eliminating the carbon footprint from past chemical purchases.

Meeting the Challenge of EV Battery Recycling: An Innovative Solution

The Challenge

As the lithium-ion battery industry grows rapidly, old technology is being replaced with new. Furthermore, the lithium-ion batteries powering electric vehicles (EV’s) will not last forever. Due to degradation, the typical lifespan of an EV car battery is 10-20 years or between 100,000 and 200,000 miles. So, what happens to these batteries when they’ve reached the end of their life?

EV Battery Recycling is a growing market in the US, especially as more batteries will reach the end of life in the coming years. 11.3 Gigawatt hours (GWh) of EV batteries reached the end of life in 2022, with that number projected to rise to 138 GWh in 2030. With the current shortage of domestically supplied battery critical materials, recycling is even more important to provide additional supply sources. One US-based battery recycler is looking to build new facilities and expand their current ones but needed the expertise of Anguil Environmental Systems to ensure a sustainable process.

This company recycles household, industrial, and EV batteries, which all have similar recycling processes. First the batteries are disassembled into smaller units, which are then mechanically separated to recover components. Afterwards, hydrometallurgical treatment recovers the metals and plastics of lithium batteries to be reused in new products. Several steps of this process produce exhausts that need to be treated.

Anguil’s engineers were brought in to design a unique system for the customer that complied with local emission regulations. Their current VOC concentrations were up to 25% LEL (Lower Explosive Limit), but a destruction rate of at least 98% was required. The combination of a saturated process stream with incoming particulate meant that special design considerations needed to be made. These will ensure a long equipment life span and minimize system downtime.

The Solution

These unique challenges lead Anguil’s team to select a Model 300 Regenerative Thermal Oxidizer (RTO). Due to the high moisture content in the customer’s airflow several parts of the system were constructed of stainless steel to provide resistance to corrosion including the process fan, diverter valve assembly, media support section and exhaust stack. An internal coating was also applied to the oxidizer chamber to provide additional protection.

To allow for processing of the spikes in VOC concentrations, a hot bypass duct system was included to bypass chamber gases directly to the exhaust stack, preventing an over-temperature condition from developing within the RTO. Prior to reaching the RTO, the process exhaust will pass through a filter in the upstream ductwork to remove any particulate.

The main process fan was sized to ensure enough inlet suction was available to overcome the planned upstream filtration and ductwork pressure losses. A local control panel near the RTO was to be included within a dedicated prefabricated room to provide protection against weather for personnel when using the panel HMI.

The Result

The RTO was chosen for this application, as it was the most cost-effective solution over direct-fired oxidizer systems and catalytic oxidizer systems. A direct-fired oxidizer would have consumed a high amount of supplemental fuel due to the high flow volume and lower VOC concentrations. A catalytic system was ruled out because of the higher initial cost due to the amount of catalyst required and the cost of periodic catalyst replacement.

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Silicon Powder Revolution: Powering the Future of Energy Storage

The Challenge

In the ever-evolving landscape of energy storage technology, the demand for efficient and sustainable solutions has intensified, prompting a significant shift in the materials utilized for lithium-ion batteries. Anode active materials (AAM) are generally made from carbon-based materials like graphite, silicon, or a combination of the two, with graphite having been the most used anode material due to its high electrical conductivity, low cost, and stable structure. However, silicon carbon-based powder offers 10 times higher capacity and up to 50% more energy density than graphite, a critical solution in this transition from lithium-ion batteries, and a sign that lithium-silicon batteries are the future of energy storage technology.

Anguil worked with a customer who has a silicon carbon anode powder manufacturing facility creating the next generation anode battery powder. The customer desired to remove the pollutants formed during the manufacturing process, and a factory site in the Northwestern United States was chosen due to the availability of hydroelectric power. In the unique production process, silane gas needed to be destroyed which forms a powder, SiO2. The particulate had to be removed to meet local air emission limits. The customer also wanted the system to have as low of a carbon footprint as possible.

The Solution

This was a challenging design due to the nature of the process. An inert process stream at a high temperature would be exiting the kilns and there were safety concerns due to the explosive nature of the pollutants and silane. An important aspect of the project was that the equipment needed to handle a significant amount of inorganic particulate that would be formed during the oxidation process. Maintaining high equipment uptime is key for both companies, so on-line cleaning was required.

To prove the efficiency of Anguil’s technology, the customer requested a pilot system on a smaller line. This pilot line design included a 700 SCFM Direct Fired Thermal Oxidizer (DFTO) that included a proprietary inlet mixer design to safely mix the explosive process exhaust with the fresh air needed for combustion. In addition to their experience with handling potentially dangerous fumes, Anguil’s expertise in inorganic dust removal and knowledge regarding handling low-density particulate was important to the customer. A dust collector was placed following the DFTO to remove the inorganic particulate. After the unit successfully ran and fulfilled the customer’s expectations, Anguil was selected as the supplier on the full-scale production lines.

Anguil was able to work with and collaborate with the kiln original equipment manufacturer (OEM) to give an integrated system on the larger lines. After the pilot line was installed and achieved the guaranteed performance requirements, Anguil was chosen to design and install two larger units on full-scale production lines for the customer.

The Result

For the full-scale production lines, Anguil designed, fabricated, and installed two (2) 9,000 SCFM DFTOs with downstream fabric filter dust collectors. These designs were created to allow for a range of operating conditions to be handled. The layout was also customized to meet site installation requirements and allow for additional future lines.

The full-scale system incorporated many design enhancements compared to the pilot line to ensure equipment uptime. Anguil performed multiple Computational Fluid Dynamics (CFD) analyses on the full-scale DFTO design and collaborated with the customer to optimize the performance and design. Anguil’s ability to provide a custom solution was critical to the customer, and much time and care were utilized to optimize the design to craft a system that can be applied on all future lines. Important design changes increased residence time to meet destruction requirements. These enhancements allowed for on-line cleaning of the heavy inflow of particulate.

The AAM market is expected to continue to grow and evolve swiftly as we discover new information about energy storage technology. Pollution from the process technologies and techniques used to produce batteries can be detrimental to our air, water, and soil if the proper abatement technologies are not applied. Fortunately, Anguil Environmental Systems offers effective, proven technologies that have been applied throughout the production chain; from material mining to powder production, anode coating, battery recycling, and component manufacturing. Anguil is well-positioned to support this ever-evolving market and develop alternate-fuel oxidizer technology.

Creating Air Pollution Control Solutions for Carbon Neutral Graphite Mining

The Challenge

The markets for lithium-ion batteries, electric vehicles, and fuel cells are increasing exponentially, meaning the demand for graphite is higher than ever before. Lithium-ion batteries consist of four components: electrolyte, separator, cathode, and anode. Every component is essential to the battery, meaning it cannot function without one. Graphite is the single largest mineral component of the battery, making it an essential material in manufacturing lithium-ion batteries and electric vehicles that rely on batteries.

The anode stores lithium ions when the battery is being charged and then releases them, allowing currents to pass through an external circuit. Graphite powder is currently the most-used anode material due to its composition and storage capacity.

With no common alternative to graphite, graphite mining has become more essential. Mining natural graphite offers lower carbon emissions than the energy-intensive production of synthetic graphite. New companies are being formed and existing companies are ramping up production by creating new mines and production lines. However, more mining activity leads to more emissions and a greater carbon footprint for these companies.

Anguil Environmental Systems recently helped lower carbon emissions from the production of battery material with the installation of air pollution control equipment at a natural graphite mine in North America. Increased government regulation on emissions and the desire to create a sustainable product motivated this company to install a custom-designed system from Anguil.

The Solution

Increasing government regulations on emissions often drives companies to install air pollution control equipment. However, more companies are being motivated by ESGs, or Environmental, Social, Governance, which is an assessment of a company’s ability to limit its environmental and social impact. This graphite mining company is ahead of many, as they have already achieved carbon neutrality and are hoping to be Net Zero by 2030. So, when installing new production lines, it was no question that they were going to install pollution control equipment.

This specific plant produces high-quality Coated Spherical Purified Graphite (CSPG) for lithium-ion battery anodes. Due to the unique nature of their process, Anguil recommended a demonstration line, or pilot unit, to prove system effectiveness and efficiency for the specific graphite qualities at the processing plant. The emissions to be treated were from a pusher furnace/kiln that processed graphite and pitch. The furnace exhaust was inert (no oxygen) and at a high temperature, with the possibility of condensable organics. The furnace hood exhausts, which would contain oxygen and trace VOCs, also needed to be sent to the oxidizer. This meant Anguil’s engineers had to ensure good mixing of the two process streams with an additional third fresh air stream to be added to ensure the proper oxygen needed for oxidation. The equipment selected was a 500 SCFM (790 Nm3/h) Direct Fired Thermal Oxidizer (DFTO), which is capable of over 99.5% VOC destruction efficiency. The DFTO was coupled with a proprietary inlet mixer to alleviate the mixing and condensation concerns. The mixer was designed to minimize cold spots when the air streams were introduced to the process stream.

Anguil utilized CFD modeling to ensure the proposed design would have proper mixing and flow distribution to maintain emission destruction requirements and efficiency parameters.

An increased residence time in the combustion chamber was also added to meet destruction requirements. A horizontal combustion chamber allowed for the system to be installed above the furnace inside the facility. An induced draft configuration was incorporated to keep the oxidizer system operating under negative pressure for health and safety concerns. Anguil worked closely with the furnace supplier to ensure a seamless integration.

The Result

The plant runs on renewable electric hydropower, which meant the energy use of the equipment had to be minimal. The DFTO operates on propane that is used for the initial equipment startup, and to maintain a pilot flame only. The high VOC content in the process means that little to no supplement fuel is needed to keep the oxidizer at operating temperature during normal operation. This results in essentially no additional greenhouse gas emissions to reach their goal of carbon neutrality. The burner will be operating on pilot flame only during normal production and the DFTO controls allow the oxidizer to automatically adjust to changing inlet conditions to ensure the minimum amount of supplemental fuel is used. Anguil is working on a lower carbon footprint oxidizer for the future full-scale production lines that will be implemented at this site. The new design will eliminate the carbon dioxide formed from a typical gas-fired burner. Despite facing obstacles due to COVID-19, Anguil was able to install a high-quality system and offer professional support during the installation and commissioning stage. Anguil’s extensive network of service engineers was able to overcome the difficulties of travel during the COVID lockdown period.

As the company gears up to create full-scale production lines, the Anguil air pollution equipment will keep emissions below government regulations. Anguil technology can be adapted to meet customers’ energy needs and help them transition to even lower carbon footprint-oxidizers in the future.

Planning for Increased Can Capacity Pays Dividends

The Challenge

A US-based can manufacturer recently upgraded their regenerative thermal oxidizer (RTO) in order to increase the maximum flow to the unit. The original oxidizer was designed and installed by Anguil back in 2015, with the intent to eventually upgrade. Anguil was able to successfully retrofit the equipment while overcoming the challenges that ensued. Through calculations and cost comparisons provided by Anguil, the customer was able to make practical, cost-effective, and environmentally friendly decisions to meet their specific needs.

Though the company has several Anguil units across the country, the retrofit was performed on an oxidizer with an upstream dust collector at a plant in the Midwest. An Anguil RTO can capture and destroy over 99% of the volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) emitted from the ovens and driers that are often used in can-making, coil coating, or metal painting. Emission destruction is achieved through the process of high-temperature thermal oxidation, converting the pollutants to carbon dioxide and water vapor while reusing the thermal energy generated to reduce operating costs.

“The plant had always planned to add additional lines so there was capacity built into the oxidizer and dust collector,” said Charlie Fields, an aftermarket application engineer at Anguil. The additional coating line the customer wished to add would send a total of 41,500 standard cubic feet per minute (SCFM) to the equipment, an increase of over 20,000 SCFM. Though the equipment was oversized initially to accommodate added flow, “the new production line would have exceeded the capacity of the RTO,” Fields continued.

The Solution

To solve the issue, Anguil proposed multiple options to the can manufacturer. The first option was to install an additional, smaller oxidizer to handle the additional flow. However, this would have been costly to purchase and operate, as the plant would have had two different-sized RTOs. Furthermore, there was no available space to install a second RTO. The second option was to install a new, larger oxidizer to handle the total flow. However, removing an existing, working oxidizer and decommissioning it would be very expensive, along with the cost of buying and installing a much larger oxidizer. This option would have also presented production challenges as many can making plants cannot run without abatement systems in place. After collaboration between Anguil and the can maker, they decided on a third option.

The Result

The chosen solution was to install a concentrator wheel to concentrate the cool air streams to allow for more capacity in the RTO. The selected 15,000 SCFM concentrator wheel concentrates the flow from an existing dust collector and sends 1,500 SCFM of VOC-laden air to the RTO inlet. This ensures that all the lines can be used simultaneously. “We decided to run all the cool streams through the wheel to concentrate them and provide additional capacity now and in the future,” Fields said. “All the hot sources were run directly to the RTO.” The operating costs of this RTO/concentrator system were much lower than those of the other proposed systems: small/large RTO system and 1 large RTO system.

Once the retrofit decision was made, Anguil provided a turnkey project that included design, engineering, equipment selection, fabrication, installation, and startup services. With the purchase of an Anguil installation, the can manufacturer received a field service team to provide support and get the project finished and the equipment online.

Keeping Battery Production Profitable and Green

Batteries have become a key contributor in the world’s energy transition and critical in the effort to slow climate change. As a result, battery manufacturing technologies and techniques are constantly evolving as producers look to remain competitive, increase storage capacity, and improve efficiency while decreasing battery size and weight. For instance, some producers are turning to a silicone-based anode material to increase battery output and reduce cost; others are exploring mining lithium from seawater to alleviate supply issues. When combined with an unprecedented increase in demand and subsequent production increases, it is fair to say that manufacturers are in a constant state of change. And it is not slowing down: some experts estimate the lithium-ion battery market alone will expand 18% by 2030. In short, we need more energy storage, in smaller batteries, at lower costs.

Lithium-ion batteries are considered the most energy-dense and longest-lasting rechargeable batteries currently available. The process of making them varies, but in general it consists of mixing raw materials followed by a series of coating, laminating, drying, cutting, winding, welding, sealing, forming, pre-charging, and degassing before a final test. However, when battery advancements occur, many of these existing production inputs and manufacturing practices need to change quickly. This can include raw material adjustments, production equipment modifications, or a change in coating techniques, just to name a few. The pollution control technologies employed at the battery manufacturing facilities are also affected by the upstream changes but are often an afterthought by plant personnel.

Regulated by most state and federal agencies, Volatile Organic Compounds, or VOCs, are pollutants generated in many manufacturing processes. The battery industry is accustomed to these harmful byproducts and the compliance hurdles that accompany them. The organic vapors are dangerous to humans when inhaled in quantities over an extended period. They also interrupt and destroy natural plant processes and play a significant role in the formation of ozone and smog. Hazardous Air Pollutants (HAPs) are a classification of VOCs with additional harmful properties, including potentially causing birth defects, nervous system damage, and even death in concentrated levels; HAPs are also a regulated pollutant from battery manufacturing.

One synthetic graphite anode powder manufacturer was modifying their furnaces to accommodate new products for lithium-ion battery manufacturing. Because their production facility was in a non-attainment area, per the United States Environmental Protection Agency (EPA), air quality standards required them to take special precautions. This meant a Title V permit would be required, as they have the potential to emit more than 100 tons per year (TPY) of VOCs, more than 10 TPY of any single HAP, or more than 25 TPY of any combination of HAPs.

This manufacturing plant in the United States produces high-performance anode material for lithium-ion batteries. A key component of lithium-ion batteries is the anode which stores and releases the lithium ions. Graphite is currently the most commonly used anode material. The process starts with a petroleum coke, which is formed into a synthetic graphite through graphitization. During operation, between 12 to 18 graphite furnaces, which are modular in construction and electrically heated utilizing local hydropower, are needed to meet the production demands.

This facility was no stranger to environmental stewardship. In years prior, they completed an Environmental Assessment to secure financial assistance from the Department of Energy and participate in the American Recovery and Reinvestment Act, which aims to accelerate the development and production of electric-drive vehicles systems to substantially reduce the United States’ consumption of petroleum. In fact, the site itself remains nearly 70% greenspace today.

In keeping with the company’s sustainability goals, they immediately began the search for an effective and efficient air pollution control system. As is the case with many manufacturing operations, process emissions are best destroyed using thermal and catalytic oxidation technologies where time, temperature, and turbulence convert VOCs and HAPs to heat, water vapor, and small amounts of carbon dioxide (CO₂).

Widely considered the most energy-efficient oxidation technology, the Regenerative Thermal Oxidizer (RTO) uses these oxidation principles with a unique heat recovery component. Highly effective ceramic media within the oxidizer captures heat from emission combustion and reuses it to preheat incoming pollutants. The RTO also uses uniquely designed poppet valves to divert process air into and out of the oxidizer, properly balance emission loading, maintain destruction efficiency, and optimize heat recovery. Most RTOs are a two-bed design, but they can be designed in a multi-chamber configuration to accommodate larger airflows and achieve destruction efficiencies above 99.7%.

Given the emission loading and low process temperature, the company chose the RTO for its high destruction capability above 99%, and a preowned system was selected to meet their aggressive timeline for compliance. The refurbished, two-bed RTO from Anguil Environmental Systems was delivered, installed, and operational in less than ten weeks. It treats up to 5,000 standard cubic feet per minute (SCFM) of process flow containing methane, ethylene, acetylene, carbon monoxide (CO), benzene, aromatic hydrocarbons, and aliphatic organics from the electrically heated furnaces and corresponding collection hoods. Dilution air at each furnace was added to keep the overall lower explosive limit (LEL) in the duct system below 25%, per code.

The oxidizer can be operated in a bake-out mode to allow for the removal of organic build-up on the heat exchange media. At a reduced airflow, the outlet temperature is allowed to become elevated before the flow direction is switched, and this hot air vaporizes organic particulate that may have collected. Certain components of the RTO are insulated to prevent the temperature of the outer skin from increasing during bake-out.

Advanced programmable logic controls record vital oxidizer operating parameters for regulatory reporting and ethernet communications allow for remote diagnostics and service support. A variable frequency drive aids in minimizing operating cost by providing fan turn-down when only low airflow is required in the RTO.

Air pollution and greenhouse gas emissions from this facility remain extremely low due to the efficiency of the pollution control system and utilization of hydropower for the process furnaces. A preowned abatement system was selected to meet an aggressive timeline at this particular facility. However, battery manufacturers all over the world are employing various thermal oxidizer technologies to meet their unique process conditions. For instance, some silicone-based anode precursor manufacturers are utilizing direct-fired oxidizer technologies with downstream particulate control to handle silicon dioxide emissions and remain in compliance. Regardless of the process, oxidizer selection is application specific and should be based on emission constituents, process parameters, efficiency needs and regulatory requirements.