Hasanoglan Cement
Fan Technol echnology ogy Training course cou rse Germany, 2009
KHD Humboldt Wedag GmbH
Table of contents
General information/introduction information/introduction
Design of fans
Impeller design
Comparison of different control systems
Assembly / erection
Commissioning
Operation
Executed fans
Investigation of gas flow in a high pressure fan
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General information / introduction This paper is primarily meant as a practical introduction into the field of KHD-fans with the aim to facilitate handling and commissioning, maintenance and elimination of trouble during operation.
KHD Humboldt Wedag GmbH mainly manufactures fans for the cement industry and can look back on a long tradition and experience and carry on this basis.
Thanks to their robust construction the KHD fans are designed for especially rough operating conditions at a high degree of operational safety. For all materials used great importance is attached to good weldability and high toughness.
The fields of application of the KHD fans primarily are the transport of hot gases and dusts.
e.g. as: Raw meal fans with high dusts loads and high differential pressures
Preheater fans, suitable for temperatures up to 450 °C with narrow blades for operation at low vibrations and at the same time low tendency to form accretions and high efficiency.
Dedusting fans for kiln waste gas dedusting, cooler- and bypass dedusting for large volumetric flows at low pressures Fans for cement grinding with particularly abrasive wear
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Design of fans The fans essentially consist of a centrifugal/radial ventilator wheel (blades backward curved) on a shaft carried in antifriction bearings and the housing designed as guiding attachment. The conveying rate can be controlled with the aid of inlet vane vane control/louvre damper and/or speed controller. However a further option are the losses through a throttle flap arranged upstream in the tube. This option is readily made use of for raw meal fans with constant operation. The impeller and shaft are dynamically balanced (ISO DIN 1940 G3,4). Our workshop can balance impellers up to a diameter of approx. 4.5 m and a maximum weight of 12 t. The shafts are manufactured up to tip widths of 7.8 m. The impellers are designed for a maximum circumferential speed of 185 m/s. The materials of the impellers can be used at operating temperatures up to 450 °C. Regarding the strength the shafts are designed with high safeties and are, according to customer requests, designed with the predetermined distances to the critical natural frequency, at least, however, with factor 1.4 (sub-critical operation). Mainly used are oil-lubricated self-aligning roller bearings. Deviating from this in some cases also grease-lubricated bearings. These bearings have a simple design and require no separate cooling (oil cooling, air cooling) and can be used at high temperatures. The bearings can easily be exchanged. Oil lubrication by means of an oil supply ring ensures a low-cost, trouble-free and low-maintenance operation. Due to simple antifriction bearings the fan can be operated with very low speeds which is not permitted for plain bearings on account of the hydrodynamical lubrication principle which could also result in increased wear. The antifriction bearings (self-aligning roller bearings) are designed for a service life of at least 100000 h.
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As required, the arrangement is made rigid or flexible (by means of spring element). Whereas the fans in high buildings are mainly arranged flexibly (reduction of the dynamical forces to approx. 3 %), fans set up directly on the foundation can be rigidly anchored for the purpose of simplifying the technique and minimizing of the costs. The fans are distinguished according to the different pressure differences into low-pressure/medium pressure and high-pressure fans (up to 185 m/s circumferential speed). High-pressure fans with self-aligning roller bearings are exclusively designed with cylindrical seat (no tensioning sleeves). Depending on use, size and speed the fans are built single-inlet or double-inlet, for which the single-inlet low-pressure fans up to a diameter of 3.35 m are designed overhung; highpressure fans (with narrow wheels) are designed overhung up to a diameter of 3.15 m for a max. speed of 1000 1/min. Moreover, the fan shafts are supported on either side. Low capacities can be realized with the aid of belt drive for the purpose of simple speed variation. Because of easier handling/maintenance and for reasons of safety capacities >400 kW are only transmitted with low-maintenance couplings and/or spur gearings. Low-pressure/medium pressure fans are mainly used as dedusting fans and due to the high amount of air these are largely of twin-stream design with low speeds.
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Advantage of single-inlet type: low cost, utilization of tumbling effect (Koriolis force) only one inlet Advantage of double-inlet type: high air capacity at low density, lower circumferential speed of the impeller than in case of an equivalent single-inlet impeller. Lower axial forces. Lower motor costs. The kiln- and cooler dedusting fans are of double-inlet type on account of the high amount of air. The classifier fan (cement grinding) is of single-inlet and overhung type due to the high wear which ensures that the fan shaft is not exposed to wear caused by the material. By ample dimensioning of the impeller , wear at the armoured impeller is low and has an long service life also in case of increased dust.
Given below is a short survey of the fans presently taken into operation and those which will be taken into operation.
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KHD Humboldt Wedag GmbH Design of fans Preheater fan Hasanoglan HKSK212/355
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KHD Humboldt Wedag GmbH
Data of performance Preheater-fan: volume flow V: 8690 m³/min pressure difference ∆pst: 84 mbar pressure difference ∆pt: 87,36 mbar temperature °C: 320°C speed: 960 1/min power consumption Pw: 1700 kW motor power: 1785 kW at 330 up to 960 1/min content of dust: 25 g/m³ density at entree: 0,519 kg/m³
drive: control system: installation: bearing: vibration control: temperature monitoring:
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coupling frequency control spring units on both sides, pendular roller bearing both sides PT100 (both sides)
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Cooler dedusting fan Zaveh Torbat ZMB1800/2500
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Datas of performance cooler dedusting-fan: volume flow V: 9155 m³/min pressure difference ∆pst: 20 mbar pressure difference ∆pt: 22,53 mbar temperature °C: 240 °C speed: 695 1/min power consumption Pw: 437 kW motor power: 450 kW at 330 up to 730 1/min content of dust: 0,05 g/m³ density at entree: 0,563 kg/m³
drive: control: installation: bearing: vibration control: temperature monitoring:
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coupling frequency control rigidly anchored both sides, pendular roller bearing both sides PT100 (both sides)
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Main EP fan Zaveh Torbat ZMB2000/2800
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Datas of performance Main EP-fan: volume flow V: pressure difference ∆pst: pressure difference ∆pt: temperature °C: speed n: power consumption Pw: motor power: content of dust: density at entree:
drive: speed control: installation: bearing: vibration control: temperature monitoring:
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11000 m³/min 20 mbar 23,28 mbar 105 °C 545 1/min 547 kW 580 kW at 300 up to 1000 1/min 0,05 g/m³ 0,769 kg/m³ coupling, gear drive frequency control rigidly anchored on both sides, pendular roller bearing both sides PT100 (both sides)
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Separator fan Zaveh Torbat HKF170/236
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Capacity of Separator-fan: Volume flow V: pressure difference ∆pst: pressure difference ∆pt: temperature °C: speed: power consumption Pw: motor power: content of dust: density at entree:
drive: Control system: fan installation: mounting: vibration control temperature monitoring: wear protection:
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3600 m³/min 41 mbar 41,67 mbar 90°C 970 1/min 349 kW 375 kW at 970 1/min 50 g/m³ 0,769 kg/m³ coupling inlet vane control spring units single inlet (overhung) bearing, pendular roller bearing fix bearing PT100 (2x) housing, armoured impeller
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Design of fans / materials / shafts Solid shafts
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Preheater-/ Mill fans Single –stream type
S355J2G3, P355NH, 13CrMo4-5 forged
Hollow shaft/welded construktion preheater-/ S355J2G3, P355NH, 16Mo3 Mill-/waste gas fans shaft journal forged Twin stream type tubes seamless hot rolled (EN10210)
All forged solid shafts and hollow shaft/tubes, journals with inspection certificate 3.1b EN10204 and ultrasonic testing EN10246. Hollow shafts are balanced separately according to DIN 1940 G6,3.
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Design of fans/materials/impeller Preheater fans :
13 Cr Mo 44 high-temperature steel yield points at 20 °C - 275 N/mm² at 350 °C - 216 N/mm² at 450 °C - 196 n/mm² at 500 °C - 177 N/mm²
P355NH (WStE 355) hot ductile fine- grained construction steel yield pointsat 20 °C - 304 N/mm² at 350 °C - 196 N/mm² at 400 °C - 167 N/mm² The two materials have a very high toughness and therefore are to a high degree insensitive to cracks and have a good weldability.
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Mill air circulation fans, for Raw meal mills (tube mills) :
impeller bottom and –cover plate – fine-grained constructional steel blades – highly wear-resistant material Dillidur 325L, Brinar400Cr, Creusabro8000
Vertical raw meal mills :
impeller bottom and –cover plate fine-grained constructional steel blades – armoured (depending on circumferential speed and material properties)
Cement grinding :
impeller and cover plate made of fine-grained constructional steel blades and bottom armoured (in blade zone)
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Impeller design
KHD-impellers are preferably manufactured for high differential pressures in narrow design (large ratio of impeller outer diameter relative to the blade width). This causes steady running properties, thus ensuring smooth running (minor oscillations and self stabilization due to Koriolis-effect respectively) and insensitivity especially for hot gases against dust accumulations/-accretions. KHD-impellers are manufactured with rotating inlet nozzle due to which enlarged gaps as a result of manufacturing inaccuracies cause less losses of efficiency. The range of the diameter ratio D2/D1 reaches from 0.35 – 0.71. Preheater/high-pressure fans are designed with a diameter ratio from 0.35 to 0.63. Large volumetric flows at low pressures (e.g. waste gas fans) are designed with a diameter ratio of 0.71. Blade outlet angle ß2=47°- 75° For small outlet angles the tendency to form accretions increases especially for preheater fans. The Hasanoglan preheater fan has an outlet angle of 50°. This reduces the tendency to form accretions. For waste gas fans with high air capacities at simultaneously low pressure differential preferably small outlet angles are used on account of the high efficiencies. The blade inlet angle is mainly ß1 = 35°.
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KHD Humboldt Wedag GmbH Blade shape: airfoil advantages: efficiency 0.84-0.86 minor accretions on the front Drawbacks: major manufacturing expenditure high tendency to form accretions on the rearmajor drop of efficiency (to 0.72-0.75) in case of accretions flow guide plate thin, therefore wear-through danger ensuing dust accumulations in the blade causing unbalance which is hard to eliminate Blade shape: backward curved ß1=ß2=40…45°logarithmically bent blades Advantages: efficiency 0.80-0.84 drawbacks: high manufacturing expenditure high tendency to form accretions on the rear due to small outletangle ß1=ß2 – circular blades (at Humboldt ß1=35°and ß2=50-63°) Advantages: efficiency 0.78-0.82 low manufacturing expenditure minor tendency to form accretions on the rear Blade shape: radial tip ß2=90°- circular blades Advantages: no accretions on the rear low manufacturing expenditure Drawbacks: efficiency 0.65-0.75 High tendency to form accretions at the front Blade shape: radial Advantages: no accretions on the rear negligible manufacturing expenditure Drawbacks: efficiency 0.6-0.65 high tendency to form accretions at the front
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Impeller before assembling with shaft
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Main /cooler waste gas impeller with shaft
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Double inlet preheater fan impeller
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Separator impeller with armoured blades
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Single inlet fan impeller with reinforced blades preheater fan
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Impeller during balancing
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KHD Humboldt Wedag GmbH Fabrication of hollow shaft
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Comparison of different control systems
Preheater fans are principally equipped with speed control Mill fans are principally eyquipped with throttle flap, inlet vane control or louvre damper Classifier fans: inlet vane control or speed control Inlet vane control: +simple control insensitive to trouble +for small control range low cost of power -high losses for large control ranges <0.7 V +excellently suited for classifier and mill fans (small control range) -higher sound emission -slip ring motor required / higher costs - no linear characteristic
Speed control: +large control range, low power requirement in the lower to medium control range +motor: low-priced squirrel-cage +low mechanical expenditure +low wear of impeller +no maintenance of a servodrive/guide vane controller +minor sound emission +linear control characteristic -high-cost converter -electric losses at least 6 % in the converter -additional flap for tube system possibly required
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Louvre damper
Throttle flap:
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+simple handling at maximum pressure difference and large units -higher losses than for inlet vane control at large control ratio V/Vmin +very suitable as starting aid e.g. for raw mill fans (in tube in front of fan) +low-cost solution with minor resistance (if not throttled) +low mechanic expenditure -can result in problems when starting in the non-stable range (if no speed control is existing) +few wear parts +increased noise emission -high losses upon strong throttling by additional differential pressure
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Inlet vane control
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characteristic curve of radial fan with inlet vane control
d a e h e r u s s e r P
Flow rate m³/s
Point2 with inlet vane control eta=40% With trottle flap eta=26,4%
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Variation of sound intensity level during different control systems
inlet vane control
Power consumption: C1=throttle flap
throttle flap
n o i t a i r a v l e v e l
y t i s n e p t n L i ∆ d n u o s
C2=Inlet vane control C3=speed control
speed control
Characteristic of inlet vane control (1) and linear characteristic of speed control (2)
relative volume flow
Relative volume flow
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Louvre damper
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