Application of absorption and biochemical installations for cleaning ventilation air from harmful substances in the production of mineral wool slabs

1. Technical solution of the environmental problem

The human right to a healthy environment is guaranteed by the Constitutions of the EAEU member States and Laws on Environmental Protection. Therefore, a number of industrial enterprises in the production of mineral wool slabs have to solve a complex technical problem
to prevent the release of large volumes of ventilation air polluted with harmful organic substances into the atmosphere, since exceeding the maximum permissible concentrations of harmful substances in the air negatively affects the health of both residents of nearby microdistricts and employees of the enterprise itself.

On LLC "EVROIZOL" cleaning of the ventilation air removed
from the fiber deposition chamber, it was decided to carry out in the absorption and biochemical installations (ABCI) developed in the Technopark of the Belarusian National Technical University (Minsk, Belarus). The first stage of the gas treatment complex in the number of four ABCI was put into operation in 2015.

2. Technological scheme of absorption and biochemical purification of vent air

The global trend in the field of neutralization of harmful organic substances is directed towards the wider use of biotechnologies, since the latter have a low energy intensity and a high degree of similarity to natural processes occurring in the natural environment; they are reliable in operation, do not require large labor costs and consumables for the maintenance and maintenance of equipment; practically do not have by-products that require additional technological techniques for their disposal, and in terms of capital and operating costs, they differ favorably from other methods.

Принцип работы АБХУ основан на естественных природных процессах – растворимости вредных органических веществ в технической воде с последующим их биохимическим окислением при помощи микроорганизмов-деструкторов до безвредных составляющих – Н2O and CO2. Технологическая схема биохимической очистки вентвоздуха приведена на рисунке 1.

1-fan; 2-scrubber; 3 – массообменная решетка; 4-bioreactor; 5-pump;
A-absorbent; B-ventilation air; БД-biogenic additives; СВ – compressed air. 
Figure 1 – The absorption-biochemicalinstallation arrangement

The main components of the ABCI are: scrubber, bioreactor, fan and water pump. In the scrubber, with the help of an aqueous absorbent, harmful substances are captured, and in the bioreactor, they are neutralized. In the bioreactor, the destructor microorganisms are immobilized on a carrier mounted on structural elements. The solution circulates in a closed cycle "scrubber-bioreactor", while there is no runoff to the sewer. Due to the presence of suspended substances in the vent air, the bioreactor provides a sludge removal system consisting of an airlift and a sludge collector.

General view of the standard ABCI with wind-air performance
30,000 m3/h is shown in Figure 2.

Figure 2. General view of ABCI-30

Specialists of the Institute of Microbiology of the National Academy of Sciences of Belarus have identified highly active strains of microorganisms-destructors capable of using phenol, formaldehyde and related organic substances as the only source of carbon and energy:

— Rhodococcus erythropolis 5D;

— Rhodococcus erythropolis 14Ф;

— Rhodococcus ruber88Ф.

All microorganisms-destructors used as biological loading in the absorption and biochemical installation are isolated from natural sources (natural ecological systems), i.e. they are not created artificially and do not contain artificial modifications of genomes. The destructive microorganisms have passed the toxicological examination of the Ministry of Health of the Republic of Belarus and received positive conclusions. The technology and design of the plants are protected by a Eurasian patent and have no analogues in the world market of gas cleaning equipment.

3. Experience of operation of the first stage of the gas cleaning complex

Four ABCI have been in continuous operation for more than a year
with a unit capacity of 25,000 m3/h each.
The general view of the gas cleaning complex is shown in Figure 3.
Figure 3. Absorption and biochemical plants operated by
at "EVROIZOL" LLC

The plants are equipped with an automated process control system (APCS) for gas cleaning.

The efficiency of capturing harmful substances is: phenol
and formaldehyde-75-85%, ammonia-50-80%, suspended solids-90-99%.

Every day, 6.0-9.0 m is added to the bioreactor to compensate for the losses on the natural moisture loss of the water absorbent.3 technical water and two times
per month to maintain the necessary concentrations of nutrients
(P, N, K) 3-4 kg of mineral fertilizers are applied to the bioreactor.

Among the undesirable aspects, it should be noted that during operation, the absorption solution acquired

Microbiological analysis of the water absorbent showed the number of microorganisms on the MCA medium-1.0×1010 CFU / ml, including microorganisms-destructors of the genus Rhodococcus, used in the launch of the bioreactor. The contaminating microflora was less than 7% and it is represented by microorganisms Bacillus and Pseudomonas.
The COD of the absorbent is in the range of 3-4 thousand g O2/l.

Conclusions:

Technically, the problem of cleaning complex compositions (multicomponent, high temperature, dust, the presence of condensation substances) of ventilation air removed from the fiber deposition chambers in the production of mineral wool slabs has been solved.

Очистка вентвоздуха в АБХУ позволяет не только снизить выброс вредных веществ в атмосферу до нормативных показателей, но и значительно уменьшить запаховый эффект в районе расположения предприятия. ССЫлка на видео https://youtu.be/NFwLynQajv4.