ACC TEAM The ACC team is an engineering Company specialized in Air cooled Condensers and Process Coolers activities are: Maintenance, fans, drives, bundles Cleaning and cleaning equipment Performance improvements De bottlenecking
Four ways of performance improvement 4 ways to improve perf 1. Fan performance 2. Fouling 3. Cross wind 4. Control logic Performance improvement means Financial benefit
Economics Design temp. is temperature of 100% performance. Design temperature Heat transfer is function of: a. Delta t air (in out) b. Air flow in m3/s Air flow is the only parameter, that can be controlled. More duty means more air through bundles ambient temperature 35 30 25 20 15 10 5 0 ambient temp design temp temp after aging temp with fouling required temp Series6 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 weeks of the year Fig 1 ambient temperatures in Europe over the year
What can we do 1. Remove fouling to restore the air flow 3. Optimize process control 2. Reduce fan inlet pressure loss, means more air flow, by minimizing cross winds. 4. Optimize fan performance
Removal of fouling Fouling increases air flow resistance, means less air for cooling. Heavy fouling The cleaning process Clean finned tubes Impact of water removes fouling No chemicals or detergents used
Modern way of cleaning Objective: no access on top of bundles, Automatic process Product temp. decrease Jet beams leaving the bundle
Result of cleaning with ACC s 36 Cells Measured results: 15 to 25 mbar lower backpressure For a 250 Mwe turbine generator set The power generation loss for 20 mbar loss on backpressure is 2.5 MW (only 0.5 year effective) This represents a financial loss of: 0.5 x 2.5 x 500,000 Euro = 625,000 Euro per year Cleaning costs approx. 20,000 Euro
Cross wind reduction Cross wind is the air movement under the fan inlet. This air flow creates an additional pressure loss for the fan leaving less static pressure, read airflow, for cooling Air passing under inlets Creates a suction force
The Effect Of Crosswinds Fan Induced Winds Prevailing Winds Deflected Winds Jet Stream Rapid Air flow Reduced pressure No vertical air movement Decline in fan performance
Crosswind Velocity
Custom Implementation Fan Induced Winds Prevailing Winds Deflected Winds Galebreaker wind shield diffuses jet stream Patented Galebreaker Windshield diffuses jet stream
What is the effect of this cross wind Test case: Air cooled condenser for a 232MW (200kg steam/sec.) Back pressure at the turbine exhaust: 100 mbara, Ambient 20 C 10 m/s air speed under inlets fans creates 21.8 mbar higher Back pressure, which results in 4.8 MW less power Say the average wind is 50% of 10 m/s at fan inlet level, the performance loss is 2.4 MW a yearly basis. Financial loss of 2.4 x 500,000 Euro = 1.2 Million Euro per year.
Process control Process control make the ACC more efficient and protects the ACC Against freezing
The effect of process control 3 mbar better vacuum gives 0.6 MW more power In money this means 300,000 Euro more revenue In addition good process control protects the ACC against freezing And sub cooling Sub cooling is a loss of heat that has to be compensated In the boiler
Fan power increase Without changing cabling Successfully installed in the UK Motor power is calculated with the equation: Volts x Amps x square root (3) x Cos Phi x efficiency drive. By using DC motors, with pulse control: Cos Phi will be 0.98 in stead of 0.82 Also speed can be increased Result 20% more power
Fan performance Fans create static pressure in the plenum. Bundle resistance determines air flow. Right: fan delivers 14 m3/s with a static pressure of 185Pa. Fouling makes the pressure rise to 250 PA. Air flow decreases to 8.2 m3/s. Way out is to go to an increased blade angle using more motor power.
Process parameters Shape of blades No. of blades Fan speed Static pressure Required air flow Motor power Fouling
Noise Noise is mainly produced at the blade tip of the fan. Noise depends on: Speed Blade shape Blade material No. of blades Note: reducing speed will reduce noise, but will also reduce the performance margins. Speed reduced from 190 to 160 RPM. 2.2 db Less noise 13% less efficient 14% more power Margin 4 x lower
Results refinery in The Netherlands After replacing 30 fans, production was back to 100%, during the summer of 2006. Project payback time 1 week, project costs 700,000 Euro Yearly result 15,750 million Euro,by preventing off spec products. T,amb. > 16 C