抄録
NKG corporation has been continuously developing high-efficiency centrifugal fans for industrial use for over 30 years and has established a unique design method to achieve 10%15 % improvement of fan efficiency compared with commonly known figures among Japanese industries. With the developed design, NKG has replaced as many as 500 fans to this date to save energy.
In general, improvement of impellers is still well-known measures for energy saving. However, its effect is rather limited, because dimensional matching between the impeller and the casing, which is the most important factor of high-efficiency fan, is neglected.
NKG's principle for the energy saving is to replace whole fan unit with a high-efficiency one. However, other measures for further energy saving, such as changing type of impeller, utilizing speed control system or reducing volume and pressure to reasonable levels, are applied to the replacement as the case may be. Usually, the replacement fan is so designed that the existing foundation, the inlet and outlet ducting dimensionally fit with it. Existing motors, dampers and its actuators are fully utilized also.
The study work for energy saving starts by receiving an outline drawing of the existing fan and some other data on its performance from the user. Then, to propose a quotation to the user, NKG prepares a preliminary design of the new high-efficiency fan. If the proposal is found to be acceptable to the user, for final confirmation of the energy saving effect, more detailed study, based on actual operating conditions including reduction of volume and pressure to proper levels, is performed.
Three Examples in Pulp-Paper factories :
1. Hot Air Supply Fan for Paper Dryer
Existing Fan ; 1000 m3 /min×650 mmAq. at 120°C
Replaced with a high-efficiency fan of same volume and pressure.
Result : Energy saving at 650 m3/min (normal operating point) : 27 kW (22% saving)
2. IDF for Recovery Boiler ;
Existing fan ; 5700 m3/ min×285 mmAq at 150°C
Replaced with a high-efficiency fan of reduced volume and pressure ; 5000 m3 /min ×225 mmAq at 150°C
Result ; Energy saving at 90% boiler load ; 84 kW (34% saving)
3. Exhaust fan for Lime Kiln
Existing fan (radial type); 1400 m3 min×1, 050 mmAq at 150°C
Replaced with a high-efficiency turbo fan of the same volume and pressure.
Result ; Energy saving at the rated operating point ; 156 kW (35% saving)
