Cement Energy and Environment

100% Butterlly damper ~ J c: ~ v~''"""' 0 . ., Q.. E ~50% 0 ~ u L. ., ~ - c DC drive 11. 0 Air flow rate Figure 1 Power Consumption pattem From Figure I, which gives the power consumption pattern, it is evident that maximum power saving can be achieved by installing variable drives in cooler fans. But the advan tages of replacing butterfly damper control devices wi th speed control system are offset by the following : • High cost of device • Constraints in electrical system • Constraints in plant layout • Payback period Hence installation of vane dampers as replacement for butterfl y dampers was considered for the following reasons : Fan No. RPM F9 1500 FlO 1374 Fll 1453 Fl2 943 Fl 3 990 Fl4 809 The results of investigation on possible energy saving by replacing butterfly dampers with vane dampers in the cooler section are reported in the following paragraphs. Vane Damper vs. Butterfly Damper Regarding Pressure Drop In one of the plants, all the cooler fans have variable drive and the now is reduced by speed control. The manual vane dampers which have been installed at the inlet of the cooler fans have not been put into operation yet. An experiment was conducted to assess the specific pressure drop due to the vane damper control. During the experiment the speed of the cooler fans was kept constant and the vane damper position changed from I00 per cent to 50 per cent. Table I indicates the measured pressure drops across the vane damper while reducing the flow from 100 per cent damper opening. Table 1 Pressure drop across vane dampers Flow, m 3 /min Difference Pressure Specific 100% 50% m 3 /min drop Pressure mmWG drop mmWG/ m 3 /min 705 546 !59 56 0.352 907 700 207 65 0.314 640 560 80 29 0.363 666 592 74 31 0.4 19 855 672 183 45 0.246 726 585 141 33 0.234 • Low in vestment cost (can be fabricated in local workshop) Average specific pressure drop across vane damper 0.321 • Vane dampers can be fi xed easily at fan inlet, replacing butterfly damper • No modification required in electrical and control systems In another unit, all the cooler fans have a fixed speed AC motor. The flow of cooler fans was throttled by butterfly dampers. An experiment was conducted to assess the specific press.ure drop across the butterfly damper and the results are presented in Table 2. 4