In June 2016, Russian chemical company, Polyplast launched one of the largest drying and storage complexes in Russia. Based in the city of Novomoskovsk in theTula Oblast region, the complex has a capacity of 60,000 tonnes per year, producing more than half of the country’s entire concrete additives, an activity which carries an increased risk for the environment.
 
Exterior view of Polyplast Novomoskovsk. (source: Polyplast)
 
 
The installation and implementation of project was developed jointly by Russian and German specialists from PO Ecotech and Luehg Filter GmbH & Co. K respectively. Alexandr Zaitsev, head of Polyplast’s Capital Building department, said the project had helped the company to face the dual challenge of significantly increasing the capacity of the facility and reducing the negative impact on the environment from its operations.
 
Specifications & complexities
 
The project is unusual in Russia as there are very few filter installations in the country dealing with similar exhaust gases in such large amounts. There were a number of challenges that designers had to take into account during the development and engineering of the filter system.
 
 
The facility deals with concrete additives, which are potentially harmful for the environment (source: Polyplast)
 
Alexandr Zaitsev explains: “During the design of the filter installation, we faced the complexities of combining the properties of dust in the air, especially hygroscopic and flammability, and the thermal conditions of the process, including the limitation on the permissible operating temperature of the filter cloth.” He added that Polyplast executives were encouraged by the positive feedback on the use of similar machines at some other facilities in Russia. This fact largely determined the specifications of the new installation, although its principle of operation differs significantly from filter systems used at other companies.
 
The initial stage of operation of the plant was under the daily supervision of chief engineers and, according to Polyplast, there were no significant difficulties with mastering of new equipment. The distinctive feature of the complex is the double purification system of exhaust gases from the dryers. Installation included a bag-type filter and wash scrubber of the shock-inertial type which has the ability to significantly minimize all gas emissions.
 
Mechanical purification
 
“For the treatment of industrial emissions at the new complex, we used technology relating to the mechanical purification of waste gases, namely the combined method of dry and wet purification. The equipment used for dry cleaning is a filter with a flat horizontal filtering element, while wet cleaning is conducted with a wash scrubber of the shock-inertial type,” said Zaitsev.
 
At the very beginning of the treatment process, dusty exhaust gases move from the dusting source to the installation via a crude gas inlet chamber then directly into the filter, where the filtering process itself takes place.
 
Once in the filter, dust and gas flow from the top downward, rushing through the filter elements; the flat sleeves, which are set horizontally. Dust, which is separated from the gas stream, is deposited on the outer surface of the filter elements. The restoration of the filter element, in other words, its purification from the deposited dust, is carried out in fully automatic mode with the supply of compressed air going into the interior of the flat sleeve.
 
Zaitsev explains that the dust is separated by the filter, after renewal from the surface of the sleeves and falls into the hopper filter bag. At each stage of these processes, the control of the filtering units, as well as the control of the entire machine and the operation of its particular components, are performed by the monitoring and control cabinet.
 
“The flat shape of the filter pocket allows the filter bag to be more compact. This structural feature makes it possible to achieve a large filter surface with the available size. The horizontal position of the filter bags also allows their replacement from the side of the bag,” Zaitsev added.
 
Filter design
 
He pointed out that the filter design provides the forced passage of gas downwards in the working chamber and this further improves the dust gathering in the hopper and thus excludes the unwanted result of the dust air mixture hovering in the space between the operating sleeves, which often takes place when working with light particles in vertically arranged filter sleeves.
 
At the second stage, the installation uses a wet type dust collector – a shock inertial scrubber of the Doyle type. This setting is intended to clean harmful impurities, both uniform and non-uniform, out of the exhaust gases, maximizing the cleaning of the gases before releasing them into the atmosphere.
 
Then, passing through the filter sleeves, the exhaust gases with a residual dust content of design size not more than 5 mg /m3 come to wet cleaning in a shock inertial scrubber of the Doyle type, where they undergo the final purification with an efficiency of at least 95%, which minimizes emissions into the atmosphere and adverse effects on the environment, fully eliminating the presence of specific odour emissions.
 
Zaitsev explains: “The structure and working principle of the inertial shock scrubber lies in the fact that when exhaust gases are entering the scrubbing chamber a gas stream strikes the liquid surface and creates a curtain of droplets, wherein the gas is purified. Under a sudden change of direction of the gas flow of about 180°, the suspended particulate matter, contained in the gases, penetrates the water and remains there, whilst the purified gases are sent to the gas outlet duct. Passing through the gas separation unit, the gas flow is released from the drops.”
 
Sleeve filter elements
 
According to Zaitsev, the main consumable items of the aeration machine with the sleeve filter elements are the sleeves themselves. The special sleeve carcass structure further improves the cleaning effect by the mechanical dust which drops from the surface of the sleeve. The design of the upper part of the support frame does not allow dust to accumulate in downstream of the filter bags. The design of the carcasses that support the filter bags reduces tension on the material structure of the working element, which takes place during the operation of the installation. This has a positive effect on the service life and allows long, trouble-free operation.
 
He adds: “The vertical and horizontal distance between the bars of the supporting basket or metal frame is only 25 mm. Thus, the support basket is composed of cells measuring 25 x 25 mm. This provides a low load on the sensitive filtering needle felt, which is particularly important during the operation of bag filter regeneration elements with compressed air at a pressure of 0.4-0.6 MPa.”
 
 
 
Exterior of Polyplast Novomoskovsk with technical infrastructure. (source: Polyplast)
 
 Achieving goals
 
For Polyplast, the main goal of this project was to reduce the impact of its operation on the environment as much as possible, whilst still achieving greater efficiency.  In general, this goal has been reached, because the filter system is cheaper than many European equivalents, while the actual performance has been far better than the company expected.
 
Zaitsev says: “The performance indicators of the installation unit are even higher than the design parameters suggested. The unit’s efficiency has been repeatedly confirmed by independent laboratories dealing with environmental control and monitoring.” He added that Polyplast Novomoskovsk is a socially-responsible company, particularly in terms of the environment and it uses advanced green technologies, particularly when production activities are associated with a negative impact on the environment.
 
Issues of environmental security for Novomoskovsk as a major industrial hub, as well as for Tula Oblast in general, are crucial. It’s also a growing trend in Russia as a whole as industrial companies are paying far more attention to environmental issues than they did a decade ago.
 
This is because approval by regional authorities for some projects, such as the construction of new plants, factories, warehouses and other industrial buildings, depends on strict compliance with environmental standards. Some companies insist on even stricter environmental rules, than those set by the government.
 
This filter system is a new experience for Polyplast Novomoskovsk, but a positive one. Other facilities within the company are keen to make use of machines with cyclone treatment and the wet scrubber irrigation type. The capacity of this installation is fairly significant, because, according to Zaitsev, the total combined amount of gas to be cleaned is 78,000 m3 per hour. This amounts to almost 683,700,000 m3 per year.
 
 
 
Alexandr Zaitsev, head of Polyplast’s Capital building department. (source: Polyplast)
 
Alexandr Zaitsev explains that the company is very proud of the new installation, which it considers a great success as the company has managed to significantly reduce the volume of emissions per units of finished production. He says that Polyplast has successfully addressed the environmental issues associated with the production of concrete additives, while still increasing the capacity of the complex, something that makes everyone happy.