Audit Energi Cooling System

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe AUDIT ENERGI(TKI 715/2 sks)

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe COOLING WATER TREATMENT1. General 1) Comparing with boiler system, calculation of Energy Saving is rather difficult for cooling water system since fuel oil is not used directly except chiller unit.

2) Even so, in both Industrial plant and chiller unit, Energy Saving can be realized by preventing scale formation.

3) Talking about industrial plant, cooling tower fan and circulation pump are big user of energy.

4) Talking about chiller unit, fuel consumption is drastically influenced by scale formation.

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe OPEN RECIRCULATING CWS FLOW DIAGRAMR: Recirculating Rate/Laju resirkulasi air pendingin (m3/jam)E: Evaporasi /Laju Penguapan (m3/jam)W:Windage Loss /Hilang karena angin (m3/jam)B: Forced Blowdown ( m3/jam)TB: Total Blowdown (m3/jam)HV: Holding Volume (m3) ; T1=Temperatur air Supply ; T2= Temperatur air Return....

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe RESIRKULASI (Recirculating Water), R Jumlah air yang disirkulasikan oleh pompa per jam.VOLUME SISTEM (Holding volume), HV Jumlah total air yang terdapat di dalam sistem termasuk perpipaan dan basin menara pendingin.PENGUAPAN (EVAPORASI), E Air yang hilang karena penguapan per jam HILANG KARENA ANGIN (WINDAGE LOSS), W Air yang hilang karena angin per jam { (0.05 0.2%)R }AIR BUANGAN (BLOW-DOWN WATER), B Air yang dibuang dari sistem per jam untuk mengontrol konsentrasi

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe AIR UMPAN (MAKE-UP WATER), M Jumlah air yang dimasukkan ke dalam sistem per jam.BEDA TEMPERATUR, T Perbedaan temperatur antara air pendingin masuk dan keluar Menara Pendingin (Cooling Tower)NILAI PEMEKATAN (CYCLE NUMBER), N Nilai pemekatan dari padatan terlarut di dalam air pendingin terhadap air umpan.WAKTU TINGGAL AIR (RETENTION TIME), Tr Waktu yang dibutuhkan untuk menggantikan jumlah air di dalam sistem oleh air make-up.

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (1/7)1. How to realize Energy Saving

It is essential to maintain and/or improve heat transfer surface to be clean or more clean (less scale and less corrosion) so as to realize Energy Saving. If surface condition can be improved as clean condition, it may result that Logarithms Mean Temperature Difference (LMTD) can be decreased. How to decrease LMTD? There are two possible ways. 1) Increase inlet water temperature for heat exchangers with same T same. 2) Increase T with same supply water temperature.

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (2/7)2. Adjustment of Cooling Fan

The meaning of inlet water temperature for heat exchanger being possible to increase is also to allow higher outlet temperature of circulation water. Consequently, the following adjustment of might be possible.

1) Stop operation of some fan 2) Decrease RPM of Fan motor 3) Change fan pitch (angle)

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (3/7)3. Adjustment of number Circulation pump operation

The meaning of T being possible to increase is flow rate of circulation water can be decreased.

As the results of decrease of circulation water quantity, there is a possibility to minimize number of circulation pump in operation.

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (4/7)4. Calculation example 4-1. Case-1 Circulation rate : 10,000 m3/hr (5 cell / 5 fan) Stop 1 fan Required electricity for 1 fan (2,000 m3/h) : 80 kw Electricity cost : $0,6/kw

Cost Saving = 80 x $0,6 = $48 / h = about US$34,560/month

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (5/7) 4-2. Case-2 Circulation rate : 10,000 m3/hr (5 cell / 5 fan) Decrease of fan motor RPM to be 1/2 Required electricity for 1 fan (2,000 m3/h) : 80 kw for each RPM Electricity cost : $ 0,6/kw

Cost Saving = 5 x 40 kw x $0,6 = $120 / h = about US$86,400/month

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (6/7) 4-3. Case-3 Circulation rate : 1,500 m3/hr (500 m3/h x 3 pump) Stop 1 circulation pump Required electricity for 1 pump (500 m3/h) : 40 kw Electricity cost :$ 0,6/kw

Cost Saving = 40 kw x $ 0,6 = $ 24 / h = about US$17,280/month

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe Cooling water system in Industrial Plant (7/7)5. Remarks

It is strongly recommendable to try the any modification on operation of cooling tower fan or number of circulation pump with the following caution.

1) Trial must be done after the current situation has been confirmed at good enough condition. 2) Before trial, engineering calculation by specialist must be done. 3) There is a big possibility that the scale inhibition program or/and biological fouling control must be improved by increase of dosage for this purpose.

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe

TEKNIK KIMIAPoliteknik Negeri Lhokseumawe