Developments in Wastewater Treatment and Sediment Tank Ventilation

The AERZEN turbo blower is the most recent offering from Aerzen, and has the advantages of a small footprint, extreme efficiency, and lower levels of maintenance, supported by the company’s extensive experience in this field, dating back to 1911, when it designed and marketed its first turbo blower.

At that time, a blower stage was designed based on a radial compressor, and since then, there have been few notable changes in this. However, existing turbo blowers have a great advantage in terms of reduced size and sophisticated technology in machine drive. This has enabled them to be fitted into small spaces, ensured easy speed changes and energy efficiency, and reduced the need for maintenance.

Aerzener Maschinenfabrik has now introduced brand-new Generation 5 AT turbo blowers, which are specifically intended to deal with plants that handle industrial or community biological wastewater treatment. They have striking technical specifications, such as the high-speed motors including permanent magnets, as well as simple adaptation to varying air demands between 40% and 100% at the time of the process, without the need to use mechanical adjusters.

Features

Versatility in Numbers

  • The AERZEN turbo blower can have intake flows of medium with a volume in the range of 110–9,000 m3/hour
  • It can regulate the air supply at between 40% and 100% of its maximum capacity
  • It can have nominal sizes of DN 100 to DN 300
  • It can handle overpressures of up to 1,000 mbar

Applications

  • Providing ventilation for lakes, rivers, and other water bodies
  • Treatment of wastewater

Benefits

  • The AERZEN turbo blower is designed in a way that minimizes energy consumption to the maximum possible level
  • It is robustly developed and highly reliable
  • It necessitates minimal service or maintenance
  • Its life cycle costs are very low

This machine is equipped with built-in frequency converters and also a line reactor, which are ready to connect. In addition, this motor functions at high speed but needs little energy. It is air-cooled and occupies very little space. It is regulated by speed and operates based on a specialized air-foil bearing which does not require oil or contact, and produces no vibrations. Thanks to this design, the turbo blower is highly efficient, requires little maintenance, and is durable, since the damage on its parts is lower compared to traditional blowers.

Technology: Compression Principle and Specific Work of a Radial Compression Stage

The AERZEN turbo blower works on the principle of radial compression, which produces constant compression instead of pulsatile compression. Ambient air is absorbed into the impeller along the axis and exuded again through the housing construction and impeller after changing its direction perpendicular to the intake stream, which is the radial direction, from which its name is derived.

The major difference between radial compressors and positive displacement blowers or screw compressors is this redirection. The high speed of rotation of the impeller results in the generation of kinetic energy and its transfer to the sucked-in air.

Air is pushed outward in a continuous fashion by the impeller movement, and this escaping air is channeled to a lower velocity by the cone diffusor positioned downstream, and piled up in the spiral impeller housing. The kinetic energy is converted into potential energy, resulting in the increase in air pressure.

Stated otherwise, the accelerated air molecules experience a sudden slow-down of motion within the diffusor, which makes them move in random motions, colliding at high speed with the slower air molecules that are already present within the housing. The latter thus imparts energy to the slower air molecules, leading to the compression of the air and increase in static pressure. The interaction of air in the spiral impeller and the cone diffusor housing continues until all the kinetic energy of the air is transformed to potential energy in the form of air pressure with low losses.

The principle based on which a turbo blower operates is given by Bernoulli’s Law in the form of the following equation:

     P + 0.5 pv2 = P0

This principle makes sure that a system continues to be at constant total energy if its mass flow does not change. If there is an increase in air flow speed within the system, the static pressure of the flowing air must decrease, and vice versa. This is analyzed here principally in the background of the turbo blower diffusers.

The energy can enter into this system only through the impeller as kinetic energy. Due to this fact, the impeller is the deciding factor in the use of energy. It is possible to change its blade pattern, which is vital for setting the blower stage air flow pattern. The turbo blower realizes very high flow speeds, and if it is possible to achieve this without turbulence and the ensuing energy losses, then this high-speed flow is vital in deciding the efficiency of the isentropic stage operation.

In a nutshell, the amount of work done by a radial compressor stage is dependent on the enforced mass flow of the conveyed air and the amount of energy contributed by the supplied air in the form of an increase in speed caused by the supplemented effect.

The torque acting on the shaft is given by the product of the mass flow and the ratio of inlet impeller speed to outlet impeller speed. Put differently, the product of the air or mass quantity and the isentropic conveyor height of the specific system, or the pressure increase, is the determinant of the geometry that allows the impeller and housing to function at an optimal level.

Characteristic diagram of a turbo machine

Characteristic diagram of a turbo machine

Characteristics of a Turbo Blower

Turbo blowers are represented by special maps that demonstrate the operating range of the machine when the parameters are within or above the appointed operating range. In addition, these maps generally portray the efficiency fields. The operating point can be identified within the characteristic map of each blower, making it clear when the operation is being carried out at a point within these limits and is therefore cost-effective. Below are the physical blower limits defined in terms of the four parameters:

  1. The pump limit as shown by the lowest possible throughput
  2. The choke limit or maximum throughput
  3. The maximum possible drive performance
  4. The maximum speed

Within the map, each device has a point of high isentropic efficiency, which is at the center of the map for turbo blowers. The isentropic efficiency increases with increase in pressure achieved and the specified conveyed volume flow, and vice versa. Within the operating range, the turbo blower’s design is thus crucial in determining how reliable its operation will be and how well it will fit the system to achieve cost reduction.

The blower cannot be operated beyond this range and attempts to do so may damage it. In contrast, the design could be optimized to achieve very high energy efficiencies, particularly in the medium and high volume medium flows. Moreover, it is possible to design a broad control range between the first three operating parameters—the choke limit, the pump limit, and the maximum drive performance.

The AERZEN turbo blower is built with dedicated components which are designed specifically for turbo applications, guaranteeing the highest possible current power density and very high profits within the operating range. They involve direct-drive radial blower stages without intervening drive or regulation components which increase energy losses, and field-based regulators which control the synchronous motor.

Every blower unit is equipped with standard components such as a frequency converter, a drive motor, a regulator or control system, and other unit parts needed for its operation. Constant air conveying and compression in a non-pulsatile way causes minimal noise and strain upon locations and components which could be susceptible to vibration.

W2P Wire to Process

As the AERZEN turbo blower is available as a single integrated unit that contains all necessary components, verification of the total efficiency level is sufficient to make a choice. The total efficiency level includes the partial efficiencies at all levels, such as the efficiency of the frequency converter, the motor, the control system, the motor cooling, and other components.

While comparing a turbo blower with other non-integrated machines in particular, it is important to consider the complete range of accessories and fittings such as gears, fans, and frequency converters when examining the total efficiency level of the latter, because it is likely that such add-ons will increase the total energy loss in the system.

This information has been sourced, reviewed and adapted from materials provided by Aerzener Maschinenfabrik GmbH.

For more information on this source, please visit Aerzener Maschinenfabrik GmbH.

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