Pannysylvania Magazine

With the rapid development of the food and beverage packaging industry, large quantities of Volatile Organic Compounds (VOCs) are generated during can manufacturing due to the use of coatings, inks, cleaning agents, and protective varnishes. These VOCs are mainly emitted from base coating, printing, internal coating, and various drying processes. If discharged directly without effective treatment, they can not only cause environmental pollution but also make it difficult for enterprises to comply with increasingly stringent environmental regulations. As one of the most widely used and highly efficient technologies in industrial VOCs control, the Regenerative Thermal Oxidizer (RTO) achieves more than 99% VOC removal efficiency and over 95% thermal recovery efficiency. Therefore, it has been widely applied in waste gas treatment projects within the can manufacturing industry, providing a reliable solution for stable compliance with emission standards while reducing energy consumption.

1. Overall Technical Solution for VOCs Waste Gas Treatment in the Can Manufacturing Industry

VOCs waste gas in the can manufacturing industry mainly originates from base coating, printing, internal coating, and the associated drying processes. Among these emission sources, exhaust gas from drying ovens is typically characterized by large air volume, low to medium VOC concentration, and continuous operation. Meanwhile, waste gas generated during coating and printing processes contains organic compounds such as ethyl acetate, glycol ethers, alcohols, and ketones. To address these characteristics, the industry commonly adopts a “waste gas collection system + RTO thermal oxidation system” treatment approach. In some projects, a zeolite rotor concentrator is also installed to efficiently treat large-volume, low-concentration VOC emissions while maximizing heat recovery.

1. Brief Introduction to Can Manufacturing Process

Description of Aluminum Can Production Process:(1) Uncoiling and Cupping: The Aluminum coil is uncoiled, and the sheet undergoes cupping via a specialized compound die in a cupping machine, completing blanking and cupping in one step to form cups. Cupping requires applying a lubricant to the aluminum surface to prepare for subsequent processes and reduce wear.(2) Drawing: The cupped blank is drawn to form the can body and base. The drawing process generates significant heat, requiring the addition of drawing emulsion for cooling.(3) Trimming: The top edge is trimmed to meet height specifications and ensure a smooth can mouth.(4) Cleaning: Cleaning is performed in a can washer using cleaning agents, tap water, and purified water to remove lubricants and drawing emulsion. The washer consists of seven tanks: pre-rinse, rinse, chemical cleaning, recovery, rinsing, film-forming, water wash, purified water, and lubricant tanks.(5) Drying: After cleaning, cans enter a drying oven heated by natural gas.(6) Base Coating: After drying, cans undergo base coating with resin-based paint. This process generates G1 base coating organic waste gas.(7) Drying: Base-coated cans are dried in a natural gas-fueled oven. Hot air from combustion is exchanged with fresh air through a heat exchanger, allowing the circulation of hot air into the drying chamber. This process generates G2 drying organic waste gas.(8) Printing: Cans are printed with ink and a protective varnish in a printing machine. This process generates G3 printing organic waste gas.(9) Drying: Printed cans are dried in a natural gas-fueled oven. Hot air from combustion is exchanged with fresh air through a heat exchanger, allowing the circulation of hot air into the drying chamber. This process generates G2 drying organic waste gas.(10) Internal Coating: After printing, cans undergo internal spraying with coating material to protect the inner surface. This process generates G4 internal coating organic waste gas.(11) Drying: Internally coated cans are dried in a natural gas-fueled oven. Hot air from combustion is exchanged with fresh air through a heat exchanger, allowing the circulation of hot air into the drying chamber. This process generates G2 drying organic waste gas.(12) Necking and Flanging: Cans are necked and flanged, inspected, stacked, and packaged.

2. Waste Gas Composition in the Can Manufacturing Industry

The solvent consumption listed pertains to the spraying process stage. Waste gas generated during drying has been treated separately.

3. Selection of Treatment Technology Route

3.1 Given the high air volume, relatively low concentration, complex composition, and presence of high-boiling-point VOCs in the spraying process waste gas, the treatment process adopts “Waste Gas Pretreatment + Zeolite Rotor Adsorption Concentration + Rotary RTO.”

Certain components in the waste gas are unsuitable for direct entry into the zeolite rotor concentrator due to the following reasons:

1. The waste gas contains high-boiling-point organics such as tripropylene glycol and dibutylaminoethanol, whose boiling points exceed the rotor’s desorption temperature (200–220°C). These compounds accumulate over time, saturating the rotor and reducing its efficiency and lifespan.
2. The waste gas contains N,N-dimethylethanolamine, a promoter for low-temperature resin polymerization. As the ink/coating contains substantial resin, suspended resin particles polymerize under its catalysis, clogging the rotor and impairing its efficiency and lifespan.

To address these issues, the following process flow is adopted:a. Spraying waste gas is directed to the rotor concentrator, passing through a four-stage filtration system to remove particulates, residual polymers, and high-boiling-point substances, ensuring the gas meets cleanliness standards for rotor entry.b. The four-stage filtration system comprises G4, F7, and F9 filters as the first, second, and fourth stages, respectively, with an activated carbon stage as the third to intercept tripropylene glycol, N,N-dimethylethanolamine, dibutylaminoethanol, and polymers, protecting the rotor.c. Pretreated gas enters the zeolite adsorption concentrator, where VOCs are adsorbed. The desorption fan and heat exchanger operate simultaneously, heating the desorption zone outlet gas to 200–220°C via heat exchange (using 800°C high-temperature gas from the RTO) to desorb VOCs from the rotor. The concentrated gas is continuously and steadily conveyed to the rotary RTO.d. The concentrated gas is treated in the RTO to meet emission standards.

3.2 For drying waste gas, the rotary RTO can be used directly. The average concentration is 2,000 mg/m³, with trace amounts of tar.① To mitigate tar clogging in the RTO’s lower ceramic bed, an F5 high-temperature filter is added at the fan inlet.② Despite filtration, trace tar may enter the RTO and accumulate on the lower ceramic bed over time, causing clogging and reduced efficiency. To address this:

• Large-pore ceramic beds are used at the RTO base.
• The ceramic bed layout and 12 maintenance ports facilitate cleaning.

③ A mixing box is installed at the RTO inlet to periodically preheat the waste gas using high-temperature air from the furnace. The preheated gas passes through the lower ceramic bed, carrying adhered tar into the RTO oxidation chamber for decomposition, effectively preventing tar accumulation.

4. Energy Consumption Targets

Based on a spray workshop waste gas flow rate of 75,000 m³/h and a concentration of 388 mg/m³, after 1 hour and 15 minutes, the concentrated gas reaches 5,820 mg/m³ with a flow rate of 5,000 m³/h. The average calorific value is 8,400 kcal/kg.

The heat released from oxidizing the concentrated gas can sustain RTO operation, with 144,000 kcal/h of recoverable heat. The zeolite rotor desorption requires 220,000 kcal/h, necessitating an additional 76,000 kcal/h of energy.RTO cold start time: 2 hours.

Total: 118.8 RMB/cycle

RTO Hot Start (0.8h)

Total: 71.5 RMB/cycle

Normal operation stage (full load)

Total: 117 RMB/hour

IV. Social Benefits

The use of zeolite rotor + rotary RTO equipment for treating spraying waste gas in can production achieves the following:

1. VOC emissions ≤ 30 mg/m³, complying with national and local standards.
2. Effective removal of odorous compounds from waste gas.

Media Contact
Company Name: Xi’an Yangling Yurcent Environmental Technology Co., Ltd.
Email: Send Email
Country: China
Website: https://www.yurcentrto.com/