Research And Practice On The Application Of Water-Film Dust Removal In The Veneer Drying Industry

Research and Practice On The Application Of Water-Film Dust Removal In The Veneer Drying Industry

In the veneer processing supply chain, veneer drying is a core process that determines board quality, production efficiency, and environmental compliance. The drying process primarily relies on heat generated from biomass fuel combustion, resulting in operating conditions characterized by high temperatures, high humidity, and heavy dust loads. The exhaust gas continuously generates pollutants such as fine wood fiber dust, biomass ash, and trace volatile organic compounds (VOCs). If discharged without effective treatment, these pollutants not only cause dust accumulation, equipment and pipeline blockages, and a deteriorating production environment, but also lead to non-compliance with industry emission standards, creating environmental regulatory risks. As a mature wet dust removal technology, water-film dust removal has become the mainstream process for exhaust gas purification in veneer drying lines—widely adopted by manufacturers of plywood and blockboard—due to its suitability for high-temperature, high-humidity flue gas, stable dust removal efficiency, low operation and maintenance costs, and the ability to simultaneously cool the gas and remove sulfur. This paper systematically outlines the working principles, application advantages, process adaptation strategies, key maintenance points, and industry prospects of water-film dust removal in the context of veneer drying operations, providing a technical reference for green production in the industry.

I. Characteristics of Exhaust Gas Pollution and Treatment Challenges in the Veneer Drying Industry

The characteristics of exhaust gas pollutants in the veneer drying process dictate the selection criteria for dust removal technologies and serve as the fundamental basis for the practical application of water-film dust removal. The challenges associated with pollution and its treatment manifest primarily in three aspects.

First, the dust particles possess unique properties that make treatment difficult. The dust generated during veneer drying is not composed of uniform solid particles; instead, it consists mainly of lightweight, flocculent wood fibers and fine wood powder, mixed with minute ash residues from biomass fuel combustion. These particles are characterized by small sizes, low mass, and a high tendency to remain suspended in the air. Conventional dry dust removal methods—such as cyclone separators and standard bag filters—struggle to capture micron-scale fine fibrous dust, leading to significant fugitive emissions. Furthermore, wood fibers tend to adhere to filter media, frequently causing clogging and "blinding" (caking) of the filter bags; this drastically increases equipment replacement costs and downtime for maintenance, making them unsuitable for the demands of continuous drying production.

Secondly, the flue gas conditions are complex and unstable. Veneer drying exhaust temperatures typically range from 80°C to 180°C, and the gas has extremely high humidity, carrying large amounts of water vapor alongside trace acidic gaseous pollutants. This high-temperature, high-humidity environment accelerates the aging of filter media and causes fluctuations in dust removal efficiency; it can even lead to equipment corrosion and condensation-induced pipeline blockages, severely compromising operational stability.

Thirdly, production is continuous, leaving little margin for error in operation and maintenance. Veneer drying lines often operate 24 hours a day, meaning maintenance-related shutdowns directly impact production capacity. Some high-precision dust removal systems feature complex structures, high maintenance costs, and frequent malfunctions, making them ill-suited for high-intensity continuous production; enterprises urgently require a dust removal process that offers stable operation, low failure rates, and strong adaptability.

II. Core Working Principle of Water-Film Dust Removal

Water-film dust removal is a type of wet scrubbing technology optimized for flue gas conditions characterized by high temperatures, high humidity, and fibrous dust. It purifies pollutants by leveraging the adsorption, encapsulation, and sedimentation properties of water. Ideally suited for treating veneer drying exhaust, the system features a clear workflow and a stable operating principle.

During operation, high-temperature, dust-laden flue gas from the drying line is collected under negative pressure by an induced draft fan and enters the water-film dust removal tower at a steady speed. Special internal flow-guiding structures induce a swirling motion in the gas, while a spray system continuously emits a uniform water mist, creating a continuous, dense circulating water film along the tower walls. The high-velocity flue gas makes full contact with the water film and water mist; wood fibers and dust particles within the airflow are thoroughly collided with, adsorbed, and encapsulated by water droplets, subsequently descending with the water film to the sedimentation tank at the tower base due to gravity.

Simultaneously, the high-temperature flue gas undergoes rapid cooling and dehumidification upon contact with the water film. Trace acidic harmful gases and volatile organic compounds (VOCs) are adsorbed and neutralized by the water, achieving an integrated process of dust removal, cooling, and preliminary purification. The purified flue gas passes through a dewatering device at the tower top to remove moisture and is discharged at a high altitude via the exhaust stack once it meets standards. The dust-laden wastewater from the tower base undergoes flocculation, sedimentation, and clarification before being recycled into the dust removal system; this creates a closed-loop water utilization process, eliminating pollution caused by wastewater discharge. Industry-optimized "swirl-convergence coupling" water-film dust removal equipment achieves a removal rate of over 95% for typical particulate matter from veneer drying, with high-precision models reaching up to 99.8% efficiency—fully complying with industry environmental emission standards.

III. Advantages of Water-Film Dust Removal in the Veneer Drying Industry

Compared to traditional methods such as bag-house filters and cyclone separators, water-film dust removal is well-suited to the operational conditions and characteristics of the veneer drying industry. It offers multiple core advantages in terms of practicality, cost-effectiveness, and stability, making it the industry's mainstream dust removal solution.

(i) Excellent adaptability to operating conditions and stable dust removal performance

Water-film dust removal completely avoids the drawbacks of dry dust removal systems, such as poor high-temperature resistance and susceptibility to clogging. It withstands the high-temperature, high-humidity conditions of veneer drying exhaust gas over the long term, ensuring that equipment efficiency does not degrade due to fluctuations in gas humidity or temperature. Specifically addressing the lightweight wood fiber dust characteristic of veneer drying, the encapsulation and adsorption action of the water film efficiently captures suspended fine dust. This resolves issues associated with traditional processes—such as fine dust escape and incomplete purification—thereby ensuring consistent compliance with particulate emission standards. Additionally, the equipment features a flue gas cooling function that effectively lowers exhaust temperatures, thereby protecting downstream components—such as exhaust ductwork and fans—and extending the service life of the entire exhaust treatment system.

(II) Low operating costs, suitable for the production needs of small and medium-sized enterprises (SMEs)

The veneer drying industry is dominated by small and medium-sized manufacturing enterprises that are highly sensitive to the operation and maintenance costs of environmental protection equipment. Water-film dust removal equipment features a simple structure; it lacks vulnerable consumables like filter bags or cartridges and requires no frequent part replacements, thereby significantly reducing costs associated with purchasing consumables and labor. Energy consumption is low—requiring power only for the water circulation and induced draft systems—making daily energy usage far lower than that of high-precision dry dust removal equipment. Furthermore, the integrated wastewater treatment system enables water recycling, resulting in minimal water consumption and controllable overall operating costs, making the technology well-suited for widespread adoption across the industry.

(III) Safe and stable operation, suitable for continuous production

Wood dust is flammable and explosive; dust accumulation inside dry dust removal equipment can create safety hazards. In contrast, water-film dust removal uses water as the purification medium throughout the process, effectively preventing dry dust accumulation and eliminating the risk of dust explosions at the source, thereby ensuring greater production safety. The equipment lacks delicate, easily damaged components and boasts high load tolerance, allowing for stable, 24-hour continuous operation. It is ideally suited for the uninterrupted production modes typical of veneer drying, with minimal downtime due to malfunctions, ensuring stable production line output.

(IV) Multifunctional, integrated treatment for enhanced environmental benefits

Water-film dust removal is not merely a single-function dust removal device; it simultaneously achieves dust removal, cooling, de-acidification, and odor elimination. Trace acidic gases generated by the combustion of biomass drying fuel and mild organic odors released during the drying process are initially purified through water-based adsorption and neutralization, effectively improving the production environment within the facility. Moreover, the treated exhaust gas maintains a uniform moisture content without the issue of dry dust escape, preventing dust accumulation and air pollution in the surrounding area and delivering significant overall environmental benefits. IV. Process Optimization and Application Solutions Tailored to the Industry

Based on the operating characteristics of veneer drying production lines, the industry has developed mature auxiliary processes for water-film dust removal. Through process integration and equipment optimization, purification efficiency and operational stability are further enhanced; the mainstream application model consists of "pre-treatment + water-film dust removal + water circulation/reuse."

First, a pre-treatment stage with graded filtration is installed. Before the flue gas enters the water-film dust removal tower, primary screens and cyclone pre-treatment structures capture large wood chips and coarse ash/slag. This prevents large impurities from entering the tower and clogging the spray system, thereby reducing the operational load on the main equipment. Second, an optimized swirling water-film dust removal tower is employed. Improvements to the internal flow-guiding and spray structures increase the contact area between the flue gas and the water film, enhancing the capture of fine fibrous dust and making the system suitable for low-concentration fine dust conditions. Simultaneously, an integrated flocculation-sedimentation water circulation system is utilized; dust-laden wastewater undergoes sedimentation, flocculation, and clarification before being recycled. Only a small amount of makeup water is required to compensate for losses, achieving zero wastewater discharge and aligning with green production standards.

For regions with stringent environmental regulations, enterprises can adopt a combined process of "water-film dust removal + activated carbon adsorption." The water-film dust removal stage handles the bulk of dust and acidic gas purification, while the downstream activated carbon unit adsorbs residual trace organic waste gases. This comprehensive approach meets the rigorous requirements of the *Emission Standards of Pollutants for Wood-based Panel Industry* and satisfies the environmental upgrade needs of high-end panel manufacturers.

V. Key Points for Daily Operation and Maintenance

Scientific operation and maintenance (O&M) management is crucial for ensuring the long-term, efficient operation of water-film dust removal equipment. Given the production characteristics of the veneer drying industry, core O&M efforts focus on three areas.

The first is the regular removal of impurities from the tower body and piping. Veneer dust and fibrous debris tend to accumulate at the tower base, spray nozzles, and flow-guiding baffles. Daily inspections are required to clear nozzle blockages, and the tower's sedimentation tank and flue gas inlet/outlet piping must be thoroughly desilted on a weekly basis to prevent impurity buildup from impairing water-film formation and flue gas flow. Second, standardize the management of the water circulation system. Regularly monitor the turbidity of the circulating water, timely add flocculants to purify the water, and periodically remove sludge from sedimentation tanks to prevent dust removal efficiency from dropping due to the recirculation of contaminated water; replenish water based on consumption rates to ensure a uniform and stable water film thickness.

Third, implement routine equipment inspection and maintenance. Regularly check the operating status of induced draft fans and water pumps, and inspect pipeline seals to prevent issues such as insufficient negative pressure or leaks of water and air; prioritize monitoring equipment conditions during the rainy season and periods of high-temperature production, adjusting spray water volume and fan speed promptly to accommodate operational fluctuations.

VI. Application Prospects and Future Outlook

As environmental regulations in the domestic wood-based panel industry continue to tighten and emission standards for dust and exhaust gases become increasingly stringent, green production and low-carbon emission reduction have become the core focus for the transformation and upgrading of the veneer processing industry. With its comprehensive advantages—including strong adaptability to operating conditions, stable performance, low costs, and environmental safety—water-film dust removal technology perfectly aligns with the production characteristics and environmental requirements of the veneer drying industry; it has now become the mainstream standard process for exhaust gas treatment in the sector.

In the future, water-film dust removal technology will evolve towards greater precision, intelligence, and energy efficiency. Technical upgrades—such as optimizing tower structures, precisely controlling temperature and spray patterns, and implementing intelligent water circulation regulation—will further enhance the purification efficiency for fine particulate matter and trace organic compounds. Additionally, integrating waste heat recovery technology allows for the capture of residual heat from drying exhaust gases alongside dust removal, achieving simultaneous improvements in environmental compliance and energy efficiency, thereby driving the veneer drying industry toward high-quality development characterized by low-carbon practices, standardization, and eco-friendliness.

The challenges of exhaust gas treatment in the veneer drying industry center on three key areas: capturing fine fibrous dust, adapting to high-temperature and high-humidity operating conditions, and maintaining stable, continuous production; traditional dust removal processes struggle to balance environmental performance with production efficiency. Leveraging established wet purification principles and precisely tailored to the specific pollutant characteristics and operational conditions of veneer drying, water-film dust removal technology offers a range of advantages—including high dust-removal efficiency, safety and stability, low operating costs, and environmental friendliness—thereby effectively addressing key challenges in the industry's exhaust gas treatment. Amidst the normalization of environmental regulations and the accelerating transformation and upgrading of the sector, this technology will continue to play a pivotal role, providing robust technical support for the green and sustainable development, operational safety, and environmental compliance of the veneer drying industry.