Styrene Emissions: Catalytic Oxidizer with Concentrator

Styrene Emissions: Catalytic Oxidizer with Concentrator

The Challenge

The world’s largest button manufacturer needed a pollution control system that would destroy styrene emissions and odors from a variety of plant processes. The plant was proactively seeking a cost-effective air pollution control solution to preempt future regulatory action. The main concern of the customer was the high operating cost of an emission control system.

The Solution

After thorough evaluation of several possible technology solutions, the company selected an Anguil abatement device to treat their styrene emissions. Anguil recommended a uniquely efficient solution in an  Emissions Concentrator coupled with a Catalytic Oxidizer.  A key factor in this decision was the emission concentrator’s ability to lower the volume of air that needed treatment by achieving a 10 to 1 flow rate reduction. Anguil provided the customer with a static pilot test to prove the effectiveness of the concentrator rotor on styrene. The successful results from the static test ensured the customer’s confidence in the new application of the concentrator technology to control styrene emissions.

Three main considerations guided the design of this solution: the need for an emission control system with low operating costs, the control of the high volume, low volatile organic compound (VOC) concentration of the process air stream, and the unique characteristics of styrene.

Many of the processes that emit styrene, such as boat building and FRP production, have high air flows with low VOC and styrene concentrations. Button manufacturing presents a similar problem but on a slightly smaller scale. The plant’s airflows were approximately 15,000 SCFM (24,075 Nm3/hr) with styrene concentrations ranging from 50-200 ppmv. The customer considered a Regenerative Thermal Oxidizer (RTO) and a bio-filtration system as other possible solutions. While effective in destroying styrene, both of these would have been very expensive solutions because higher air flows result in higher costs for treatment technologies. The operating costs of the RTO and the biofilter were much higher than the chosen solution because these systems had to treat the entire 15,000 SCFM (24,075 Nm3/hr) of process air.

The Result

An emissions concentrator coupled with a catalytic oxidizer reduced the process air that needed to be treated by a factor of 10. The high volume airstream, approximately 15,000 SCFM (24,075 Nm3/hr) with 50-200 ppmv of VOC, is passed through the emissions concentrator rotor where the VOCs and styrene are adsorbed in the bed, purifying the high volume air. This high volume air is then exhausted to atmosphere. The concentrator rotor rotates continuously, transporting adsorbed VOCs into a desorption section where they are desorbed from the media with a low volume heated airstream. After being desorbed from the wheel, the air volume has been reduced from 15,000 SCFM (24,075 Nm3/hr) to about 1,500 SCFM (2,407.5 Nm3/hr) and the VOC concentration of the air stream is increased to about 500- 2000 ppmv. This low volume, high pollutant-laden air is then processed by the oxidizer. By isolating and treating the lower air volume, Anguil is able to provide a system with far lower operating costs than other emission control systems.

Anguil was able to further reduce the operating cost of the system by utilizing a catalytic oxidizer to destroy the concentrated, contaminated air stream. Anguil’s experience with styrene emissions has demonstrated the easily oxidizable nature of styrene in the presence of catalyst. Catalytic oxidation systems typically achieve greater than 99% destruction of styrene with relatively low temperature requirements. An Anguil Catalytic Recuperative Oxidizer designed for 1,500 SCFM (2,407.5 Nm3/hr) was installed to process the pollutant-laden airstream with minimal auxiliary fuel consumption.

The final design consideration was to address the unique characteristics of the styrene emissions. The customer was concerned with the possibility of styrene polymerization on the rotor and subsequent system failure. Anguil had performed extensive tests to establish that certain zeolite formulations function better than others in the presence of styrene and eliminate the possibility of polymerization. However, Anguil went to the next step in order to relieve the customer’s concerns. Working closely with one of their technology partners, Anguil ran several static (live) pilot tests to prove the effectiveness and reliability of the concentrator/oxidizer technology. This testing process convinced the customer to move ahead with the Anguil solution.

Another benefit to the customer of the concentrator/oxidizer system was low maintenance cost. The zeolite material has an expected life of 10 years under continuous operation. The easy regeneration and durability of zeolite provides considerable savings over the constant maintenance and replacement required of carbon beds. Additional maintenance savings come from the durable design of the emissions concentrator. The absorbent wheel is rotated with a simple motor and belt drive, reliable components that last at least five years and require minimal maintenance.

In order to expedite installation, Anguil assembled the entire system in its manufacturing facility, allowing for customer review and inspection prior to shipment. The system was then re-erected in the field and integrated into the customer’s process. Anguil’s combination of proven experience and technologically advanced air pollution control products have led to another satisfied customer.

Fiberglass Polymer Emissions: RTO Control Technology

The Challenge

A producer and supplier of corrosion resistant piping systems was looking to improve the reliability and lower operating expenses of an existing air pollution control system at their facility. During their manufacturing process, centrifugally cast mortar pipe systems are reinforced with a fiberglass polymer. This makes the pipe ideally suited for most corrosive piping applications but also produces a significant amount of styrene emissions that need to be destroyed. Plant personnel knew that their existing 40,000 SCFM (64,200 Nm3/hr) fixed-bed concentrator and catalytic oxidizer could not handle future expansion plans and the decision was made to look for a replacement.

The Solution

After speaking with several vendors, the Regenerative Thermal Oxidizer (RTO) was selected as the best available control technology. It not only far exceeded the 95% destruction efficiency required in their permit but also dramatically reduced operating costs. The pipe manufacturer then identified what qualifications they were looking for in a solution provider:

• Styrene Experience
• Proven Performance
• Stable Supplier
• Cost-Effective Equipment
• Turnkey Capabilities

Anguil was selected based on their ability to meet these equipment and supplier requirements.

The Result

Anguil’s engineering staff worked closely with the customer throughout the design and manufacturing processes to ensure that the system precisely met their requirements and expectations. An Anguil Model 500 RTO (50,000 SCFM, 80,250 Nm3/hr) was selected based on the process airflow concentrations, destruction rate requirements, and for its overall energy-efficient operation.

Special considerations were taken to deal with the particulate in the process stream. A 48-cartridge collector was put upstream of the oxidizer to collect fiberglass pieces that could clog the RTO. Once filtered, process gases with Volatile Organic Compound (VOC) contaminants enter the oxidizer through an inlet manifold. Dual disk poppet valves direct this gas into energy recovery chambers where the process gas is preheated, then progressively heated in the ceramic beds as they move toward the combustion chamber.

The VOCs are oxidized in the combustion chamber, releasing thermal energy in the structured ceramic media beds that are in the outlet flow direction from the combustion chamber. These outlet beds are heated and the gas is cooled so that the outlet gas temperature is only slightly higher than the process inlet temperature. Fasting acting, vertical poppet valves alternate the airflow direction into the ceramic beds to maximize energy recovery within the oxidizer. The VOC oxidation and high energy recovery within the oxidizer reduces the auxiliary fuel demands and operating costs. For example, at 95% thermal energy recovery, the outlet temperature may be only 70`F (40`C) higher than the inlet process gas temperature with an RTO. The oxidizer can reach self-sustaining operation with no auxiliary fuel usage at low concentrations.

Allen Bradley Programmable Logic Controllers (PLCs) control the automatic operation of the oxidizer from startup to shutdown, so minimal operator interface is required. These controls also provide for remote telemetry to enable the system’s operation to be viewed and altered via a modem connection to reduce maintenance costs.

The customer is achieving 98% destruction rate efficiency and the oxidizer is operating extremely efficiently at 95% thermal rate efficiency. Low operating costs and equipment reliability have resulted in another satisfied Anguil customer.

Carbon Fiber: Furnace & Oven Emission Control

The Challenge

A carbon fiber company in China was faced with the challenge of selecting an emission control system for a new pilot line at their specialty fiber products facility. The line would include furnaces and three ovens, both of which would emit Carbon Monoxide (CO), Ammonia (NH3), and lethal amounts of Hydrogen Cyanide (HCN).  

The Solution

The carbon fiber processor selected Anguil Asia because of their local presence in the region and specific design for this application. Before beginning the project, the Anguil team in Asia ran an energy analysis at the facility, which ensured that the proper technology would be applied based on the destruction requirements, efficiency needs and process parameters. A Direct Fired Thermal Oxidizer (DFTO) was selected to process the furnace exhausts while a Regenerative Thermal Oxidizer (RTO) was chosen to process the oven exhausts.

The Result

To treat the higher concentration exhaust stream coming from the carbon fiber furnaces, Anguil designed a specialized multi-zone DFTO whereby the nitrogen compounds are disassociated at high temperatures in an oxygen depleted chamber. The remaining gases are quenched before moving into a secondary zone where total emission destruction efficiency is over 99% with minimal NOX generation.

The furnace exhausts typically contain tar which often causes plugging in a standard emission control device. Special design considerations were taken to reduce these maintenance concerns and improve reliability. The Anguil system introduces furnace exhaust into the DFTO with a unique inlet manifold that eliminates tar build up and plugging concerns. Anguil also provided an induced draft system for increased safety. This ensures that all of the Hydrogen Cyanide emissions would be drawn into the oxidizer for destruction, protecting the company’s employees and neighborhood from the potentially lethal gas leaking out of flanges, instruments, etc.   

Because the customer’s three oxidation ovens were electrically heated, reducing the electrical consumption was a critical objective on this project. As part of the complete energy analysis done at this facility, Anguil understood that the oxidation ovens can require a significant amount of supplemental energy to maintain temperatures from 392°F to 572°F (200°C to 300°C). The customer wanted to recover as much energy as possible from the oxidizer systems to save on the electrical power used in the ovens.  Keeping this in mind Anguil proposed several secondary heat exchangers to provide the necessary preheated makeup air back to the electrically heated ovens.   

The DFTO would be exhausting at 1600°F (870°C) so Anguil incorporated three shell and tube heat recovery bundles in series, following the oxidizer. The first two stainless steel heat exchangers would be providing preheated makeup air back to Oven #2 and Oven #3. The process exhaust downstream of that system still contained usable heat, so a third shell and tube heat exchanger was incorporated to preheat the combustion air used in the DFTO. Preheating the DFTO combustion air made the destruction device itself more energy efficient and reduced the amount of supplemental natural gas required. 

A summary of this energy recovery project is listed below:

• The shell and tube heat exchangers recover approximately 1.0 MMBTU/h (293 kW/h) to be returned as preheated air back to Oven #2 and Oven #3
• The estimated payback on the heat exchangers is less than 3 months
• The shell and tube heat exchanger to preheat combustion air to the DFTO will recover approximately 0.18 MMBTU/h (53 kW/h)
• The estimated payback on the combustion air heat exchanger is less than 7 months (based on a natural gas cost of $10.00/MMBTU and assuming 24 hour/day operation)

To treat the higher flow, lower concentration exhaust from the ovens, Anguil selected an RTO. This type of oxidizer is capable of 98-99%+ destruction efficiency with very low operating costs compared to other emission abatement technologies. With achievable thermal efficiency over 96% the RTO is capable of operating with little to no supplemental fuel use.

During operation the emission laden process gas enters the RTO through an inlet manifold to flow control poppet valves that direct this gas into energy recovery chambers to be preheated. The process gas and contaminants are progressively heated in the ceramic media beds as they move toward the combustion chamber.

Once oxidized in the combustion chamber, the hot purified air releases thermal energy as it passes through the media bed in the outlet flow direction. The outlet bed is heated and the gas is cooled so that the stack temperature is only slightly higher than the process inlet temperature. Poppet valves alternate the airflow direction into the media beds to maximize energy recovery within the oxidizer.

In keeping with the overall goal of the oxidation system to provide all of the required preheated makeup air back to the ovens, Anguil installed a secondary heat exchanger following the RTO.  The plate-type heat exchanger recovers 70+% of the RTO exhaust energy.  That preheated air is used in lieu of ambient air for the oven.   

• The plate heat exchanger will recover approximately 0.42 MMBTU/h (123 kw/h)
• The estimated payback on the heat recovery system is less than 3 months

The project resulted in an overall reduction of emissions and operating expenses for the carbon fiber company. Even on this small pilot line operation, Anguil was able to show a substantial reduction in the overall energy requirement. Due to the success of this project, Anguil will be installing air pollution control equipment on the customer’s full scale production line. The new system will also be energy efficient, keeping with Anguil’s goal of providing air pollution control equipment today to keep our customers profitable tomorrow.