Energy-efficient turbo blowers
THE cement industry is a core sector of the Indian economy. This sector accounts for 12 per cent to 15 per cent of the total energy consumed by the industrial sector. Being an energy-intensive industry, typically energy cost in this segment of industry accounts for 5060 per cent of the total production costs. Major portion of electrical energy is consumed to run the auxiliary equipment such as kiln motors, combustion air blowers and fuel supply, etc, to sustain the pyro-process. Godrej brought the state-of-the-art technology from Aerzen, Germany, a pioneer in air blowers, is celebrating its 150th anniversary. Aerzen is regarded as the best for their most reliable and energy efficient air blowers in the world.
Below chart shows transition in the technology of air blowers and increasing trend in energy efficiency. Aerzen turbo blowers save more than 40 per cent power over the conventional twin lobe blowers.
Core components Permanent Magnet Motor:
a) Power required only to rotate and not for magnetising of rotor; b) can be started and stopped any number of times; c) high efficiency even at part load.
No gear box: No transmission loss due to direct drive, no lubrication and no oil-seals required.
Built-in variable speed drive for achieving high speed, smooth starts (reduced starting current <5 per cent of full load current) and energy efficient capacity control over minimum to maximum operating range.
Air foils bearings for high speed operation (used in jet engines).
- Oil free air - over satisfying ISO 8573-1 class 0 requirements.
- Low noise: less than 80 dB against 100 dB of PD blowers..
- Entire range is air-cooled and no need of water for cooling..
Conventional roots/twin lobe rotary PD blowers, have serious problems such as high levels of noise and vibration and frequent oil leakage (lubricant oil) deteriorating the work environment in the field. Above all, they have very poor system efficiency. Aerzen turbo blowers employ the high precision machined cast impellers, hydrodynamic air foil bearings (air-lubricated), highly efficient permanent magnet motors and sensor-less Invertor drives, which eliminate the complicated gear trains or pulley and belt to provide considerable energy savings without much scheduled maintenance and with very low level of noise.
Permanent magnet (PM) motor
The Aerzen turbo blower uses permanent magnet motors which have very high efficiency over the entire range of operation as compared to induction motors. No magnetising power is necessary: Since the rotor of the motor has built-in permanent magnet, the power is required only to rotate the shaft. Smaller rotor means less friction loss: With the rotor being specifically designed to rotate at high speed, the size of the rotor is small. Also, the rotor being made of titanium and inconel alloy is lighter in weight. Because of these two factors the twisting torque is comparatively very small.
Lower heat generation means less cooling loss: The high electric grade material and high rotating speed produce less heat and hence cooling energy required is comparatively lower.
No slip means high efficiency even at part load condition: PM motor is a synchronous motor, which has no slip and hence power factor is high. The efficiency is consistently maintained more than 95 per cent from full load to partial load conditions.
Air foil bearings
Air bearings have advantages over conventional ball or mechanical bearings in that the shaft does not come in any physical contacts, which means that no lubricant oils are required, there are no mechanical energy losses and there are no abrasions caused by physical contacts while the shaft is in motion. The shaft of the motor is suspended in air since the shape of the shaft transforms kinetic energy into pressure energy while the shaft is spinning. This extraordinary design eliminates the need to pump air into the machinery from external air pumps since it can self-levitate. This increases energy efficiency.
Impeller design capabilities The impeller is directly mounted on the shaft of the motor. The impeller is made up of machined cast stainless steel material 17-4 ph which is equivalent to grade SUS630 having high structural strength. The profile is backward leaning to provide larger flow capacity, wide operating flow range and high efficiency.
The impeller alone is first dynamically balanced and again dynamically balanced together after mounting on the shaft.
User selectable control modes Different applications in cement industry demand different types of controls. Aerzen turbo has all the kinds of controls built-in and any one type can be selected at site as per the requirement of application: constant flow; constant pressure; constant power, and DO. control. During optimum selection of blower, the calculation software plots various operating points of flow and pressure w.r.t. actual ambient conditions and accurately predicts the total input power as well as æwire-to-airÆ efficiency at every point.
Case studies A renowned cement company in India decided to improve their energy efficiency during expansion of their plant production capacity and enhancement of the kiln. For the application of coal transfer from coal mill to kiln burner main firing, rated flow capacity of earlier blower was 36-m3/min at 0.4 bar G to 0.5 bar G pressure, whereas, the new capacity of blower was required to provide flow output of more than 70-m3/min at 0.6 bar G pressure. For this purpose, they installed Aerzen turbo blower. Another progressive Indian cement company replaced their existing reciprocating compressors and installed Aerzen turbo blowers of similar capacity to achieve energy savings in kiln jet air burner pipe application. The table below shows the result of 67 per cent power savings after actual measurement was carried out.Godrej carries out measurement of power, flow and pressure to arrive at the prevailing conditions for specific applications. Based on scientific calculator software, power is calculated at various operating points of flow and pressure at actual ambient weather conditions to select a right size of Aerzen turbo blower. Based on this, Godrej provides guaranteed energy savings, which are demonstrated upon installation of the Aerzen turbo blowers.