 | | More air with up to 30 % less energy | |
|  |
Operating costs and energy consumption in waster water treatment plants have been steadily rising in recent years due to increased regulation regarding health and water protection. Soaring energy prices and the threat of apparent climate change are also adding to the pressure to make savings without compromising the quality of waste water treatment. Help is at hand however, as modern compressed air engineering provides a wide range of energy saving solutions that meet all of these needs. The motto “Wherever there’s consumption, there are savings to be made” also holds true for water treatment plants, as with so many others, when it comes to energy efficiency and cost optimisation. The regional authorities for environmental protection in Baden-Württemberg, Germany, estimate that water treatment plants could achieve potential energy savings of between 20 and 30 percent1. In order to tap into this potential however, a wide range of measures would have to be taken and would have to work in close harmony with one another. One such measure includes reduction of energy consumption for clarifier aeration. This is where modern rotary blower technology can play a key role. Comprehensive Analysis and Planning In order to tap into the full potential of a blower system and ensure optimized compressed air availability, it is essential to view the system as a whole and to use efficient components. It is therefore necessary to first determine the current demand requirement and also to forecast potential future demand by carrying out detailed analysis. Modern computer-aided processes, such as Kaeser's ADA (Air Demand Analysis) technology, are relatively easy to implement and achieve impressive results. The data from the air demand analysis is then evaluated with the help of specialised planning software ('Kaeser Energy Saving System', or 'KESS' for short) to determine the best overall system solution – KESS, for example, is able to simulate various alternative systems and compares these with the existing installation. It is clear therefore that the planning phase lays the foundations for system cost optimisation and energy efficiency: Careful planning alone can lead to energy savings of more than 17 percent compared with standard system solutions. Other measures include: drawing in blower air from the ambient surroundings, using correctly sized piping (minimises pressure losses) and fans, appropriate blower configuration and efficient control systems governed by a master compressed air management system. Optimised Components a) Efficient Rotary Blowers Optimised system components are the key to a reliable and efficient compressed air supply. ‘Compact’ series rotary blowers from Kaeser are a perfect example (Image): Meticulous design and logical component layout make maintenance work simple, as these units are operated and accessed from the front. This not only significantly reduces maintenance costs, but also means that these units can be placed directly next to each other to maximise use of space. Each model is fitted with an energy-saving EU-eff1/EPACT rated motor2 as standard and features omega profile rotors and a specially designed housing to ensure low energy consumption and outstanding performance. The high thermal tolerance of the blocks allows high inlet temperatures and enables an exceptionally wide control range for units with variable speed control. Further energy savings are possible as the blower can be regulated to provide very low delivery volumes.
The motor and blower block are connected via a V-belt drive system equipped with an automatic tensioning device to ensure constant and efficient power transmission.
Modern blower design and technology provides exceptional performance even with regards to sound emissions and pulsation of the conveying air. Wide-spectrum adsorption silencers on the intake and pressure sides now enable highly effective sound and pulsation damping - the silencers are fully effective throughout the entire frequency spectrum, i.e. at all speeds and duty points. Specially designed sound enclosures – even for large systems with air deliveries over 3000 m³/h – keep sound levels to an absolute minimum and blowers are also available as super-soundproofed versions.
In addition, the conveying and motor-cooling air are drawn in separately from outside of the system cabinet, which enhances both cooling and energy efficiency: This approach prevents the air from being pre-warmed and consequently enables greater flow capacity for the same drive power. Furthermore, by using air that has been drawn in from outside of the blower unit, and which has therefore not been subjected to pre-warming, the lubrication intervals for the motor bearings are much longer, which again reduces maintenance costs. Irrespective of blower speed, sufficient cooling of the blower block and motor is achieved through forced ventilation of the blower cabinet. With variable speed units therefore, this enables the available frequency range to be used to its full potential, resulting in corresponding energy savings. b) Energy-saving control systems Internal control systems and techniques (e.g. frequency control) now also allow blowers to operate efficiently at partial load, whilst master compressed air management systems, such as the “Sigma Air Manager“, enable several blower units to operate in unison with maximum efficiency. These systems also carry out detailed performance monitoring and record data for inspection and control purposes.
All of these measures can help to reduce the energy consumption of a water treatment plant’s blower air supply by up to 30 percent.
_____________________________________________ 1: Cornel, Peter: Sparpotenziale im Klärwerksbetrieb (Savings Potential in Water Treatment Plants). In: Umweltmagazin, Jan. – Febr. (2007), S. 18
2: These motors conform to the stringent efficiency requirements of the US “Energy Policy Conservation Act“ (EPACT) and to “EU-eff1“, an equivalent voluntary agreement between European electrical motor manufacturers. |
