EXPERIENCE IN THE OPERATION OF ABSORPTION AND BIOCHEMICAL PLANTS (ABCI) FOR THE PURIFICATION OF VENT AIR FROM FORMALDEHYDE AT JSC " VITSEBSKDREV»
N. N. Vit, Chief Engineer " Industrial ecological systems»
Glushen E. M., Candidate of Biological Sciences, Head of the Department. Laboratory of Environmental Technologies of the National Research University " Institute of Microbiology of the National Academy of Sciences of Belarus»
Groshev I. M., Candidate of Technical Sciences, Associate Professor, Head of TSL of JSC " Vitsebskdrev»
The technological processes of manufacturing chipboard and MDF boards are accompanied by the release of harmful organic substances into the air, the most common and toxic of which is formaldehyde. Technically, the problem of preventing the release of formaldehyde into the atmosphere is solved with the help of ABCI (Fig. 1).
- How ABCI works
Ventilation air purification in absorption and biochemical plants (Fig. 2) is based on natural processes. The first is that most harmful volatile organic compounds( VOCs), including formaldehyde, are highly soluble in industrial water. The second is based on the ability of specially selected and adapted microorganisms to use organic substances dissolved in water as food sources. The collection of microorganisms-destructors of the Laboratory of Environmental Biotechnologies of the Institute of Microbiology of the National Academy of Sciences of Belarus includes more than 500 strains capable of degradation of a wide range of volatile organic compounds.
In the process of their consumption by microorganisms, complete mineralization occurs with the formation of water and carbon dioxide. In a scrubber with a movable ball nozzle, harmful substances are captured using an aqueous absorbent, and in a bioreactor, they are neutralized. Microorganisms are introduced into the bioreactor once before the start of operation of the plant in the form of concentrated biomass. Circulation of the solution in a closed circle "scrubber-bioreactor" prevents the formation of industrial runoff. The plants are equipped with a device for removing sludge and condensation substances.
2. Cleaning of vent vents from formaldehyde at JSC " Vitsebskdrev»
2.1. Selecting the cleaning method
In 2014, a line of IMAL (Italy) for the production of MDF/NDE fiberboard was installed at JSC "Vitsebskdrev". During the pre-commissioning work, due to the use of urea resin as a binder during dry pressing, formaldehyde emission was observed in the air environment of the workshop, which required the use of ventilation and exhaust ventilation with a capacity of 90,000 m.3 of air per hour. Due to the high background concentrations of formaldehyde in the surface layer in the territories adjacent to the enterprise, the project organization justified the need to use gas-collecting equipment. When choosing the cleaning method, it was also necessary to take into account the presence of methanol, ammonia, water and oil vapors, wood fibers and resinous substances in the vent air. The administration of the enterprise considered the possibility of using plasma-catalytic or absorption-biochemical  purification methods. The choice of a supplier of gas cleaning equipment was determined by information about the negative experience of solving this environmental problem at JSC "Cherepovets Plywood and Furniture Plant" through the use of plasma-catalytic gas convectors, while the degree of formaldehyde neutralization did not exceed 10%. Retrofitting the gas convectors with two additional stages of cleaning (dedusting and cooling) did not change the situation. Gas-discharge cells of convectors lost their functionality during several hours of operation due to the deposition of condensation and suspended substances on their surface . Due to the lack of functionality, the gas convectors were replaced with two ABCI (Fig. 3) with a total capacity of 54,000 m for vent ai3/h, which allowed the company to reach the standards of the MPI. Additionally, waste water containing formaldehyde is fed to the ABCI water absorbent regeneration system for neutralization.
2.2 Operational parameters of ABCI
UE "Industrial Ecological Systems" designed, taking into account the dimensions of the allocated room, manufactured and put into operation a gas cleaning complex (Fig.4), consisting of three ABCI with a single capacity of 30,000 m3/h. The complex is equipped with an automated control system for the technical process of gas cleaning.
Highly effective microorganisms-formaldehyde destructors Rhodotorula sp-were used to charge the bioreactors. BFF-1 and Rhodococcus opacus FF 3-1 (Fig. 5).
After two years of operation of the gas-cleaning complex, studies of absorption solutions of active bioreactors were conducted, which showed a high rate of microbial destruction of the toxicant, which is confirmed by a sufficient concentration of the biomass of microbial destructors in the absorbent (1 million cells / 1 ml of solution), a decrease in formaldehyde in the samples under study (up to 0.05 mg/ml), as well as a low COD index. The study of microorganisms from the bioreactor showed the presence of morphological features inherent in the microorganisms of the genus Rhodococcus, used when launching the bioreactor. The absorption solution also contained an acceptable amount of contaminated microflora consisting of microorganisms of the genera Bacillus and Pseudomonas.
During 5 years of operation, the passport characteristics of the complex (Table 1) remain stable.
|1||Functionality||The passport characteristics are preserved throughout the entire service life.|
|2||Stability of the regeneration system||Provide highly active strains. The concentration of microorganisms in the water absorbent is self-regulated depending on the amount of incoming nutrition (VOCs).|
|3||Efficiency||The degree of capture of formaldehyde – 75-85%, suspended solids-94-98%.|
|4||Energy consumption per 1000 m3 ventvozduha||Fan and pump power – 1.3-1.7 kW. Compressed air flow rate 1-1. 5 nm3/h.|
|5||Consumables||ЛОС поступающие с вентвоздухом. Вода технического качества для компенсации влагоуноса 0,1 – 1,5 м3/сутки. Биогенные добавки (минеральные соли) 20 – 40 кг/год.|
|6||Environmental friendliness||No by-products are formed that require additional neutralization|
|7||Maintenance||Не требуется наличие постоянного оператора.|
|8||Repair frequency||There are no components with intensive wear. The fan and water pump are subject to repair.|
It is possible to note the fire and explosion safety of ABCI. In 2018, due to a fire on the processing line, the bioreactors and the sludge sump received the products of incomplete combustion of the stove, which required additional measures to remove the sludge, while the functionality of the complex was not violated.
Absorption and biochemical installations are time-tested environmental protection equipment that can be recommended for the implementation of the national project of the Russian Federation "Ecology" in the field of atmospheric air protection at enterprises
1. Handbook of 2019 "Industrial cleaning of emissions". Appendix to the journal "Ecology of production" "Absorption and biochemical installations for cleaning ventilation air from volatile organic compounds". Yu. P. Shapovalov, A. S. Galibus, A. I. Sudarev, E. M. Glushen; pp. 2-13.
2. LesPromInfo/ "CHFMK - territory of care" 2013 No. 4 (94) p. 118-129