3.9 ENEGRY BALANCE 3.9.1 Power Balance
Due to the availability of oil palm biomass, palm oil mill itself is able to generate electricity for domestic usage and manufacturing purpose. In the designed mill, mesocarp fiber and palm shell are used as boiler fuel to generate steam. These two solid fuels alone are able to generate more than enough energy to meet the energy demands of a palm oil mill. The steam generated from boiler is sends to turbine for generating electricity. The exhaust steam is then sends to back pressure vessel for production usage. The details power consumption of each station with the total power generated from turbine in the designed palm oil mill is shown in next section.
3.9.1.1 Power Consumption
The power consumption of each station is determined based on the equipment specification. Additional 200 kWh is allocated for domestic usage including power usage in POME treatment plant and raw water treatment plant. Table X shows the power consumption for each station. The estimated total power consumption for a 30 ton FFB/hour palm oil mill is 1312.1 kWh.
Table X: Power Consumption for Each Station. N
O
MACHINERY QUANTITY POWER (kWh) TOTAL POWER (kWh)
FRUIT RECEPTION
1. Road Weighbridge 2 30 60
2. Fruit Loading Ramp 1 5.6 5.6
STERILIZATION STATION 3. Tilting Sterilizer 2 23 46 THRESHING STATION 4. Thresher 2 50 100 DIGESTION STATION 5. Digester 3 33 99 6. Screw Press 3 29 87 CLARIFICATION STATION
7. Sand Trap Tank 1 4 4
Separator
9. Crude Oil Tank 1 4 4
10. Continuous Settling Tank
1 9 9
11. Hot Water Tank 1 4 4
12. Pure Oil Tank 1 4 4
13. Oil Purifier 2 7.5 15
14. Oil Holding Tank 1 4 4
15. Vacuum Oil Dryer 1 11 11
OIL STORAGE TANK
16. Oil Storage Tank 1 7.5 7.5
17. CPO Daily Storage Tank
2 7.5 15
SLUDGE SEPARATION STATION
18. Sludge Buffer Tank 1 4.5 4.5
19. Desander 1 11 11
20. Sludge Drain Tank 1 4.5 4.5
21. Rotary Brush Strainer 1 11 11
22. Sludge Separator 2 15 30
23. Sludge Oil Tank 1 4 4
DEPERICARPING STATION 24. Cake Breaker Conveyor 1 15 15 25. Depericarper Vertical Column 1 48 48
26. Nut Polishing Drum 1 7.5 7.5
27. Pneumatic Fiber Transport System 1 75 75 KERNEL STATION 28. Nut Silo 1 4 4 29. Ripple Mill 2 11 22 30. Claybath 1 85 85
31. Bulk Kernel Silo 1 4 4
32. Wet Shell Bunker 1 4 4
BOILER STATION 33. Boiler 1 35 35 POWER STATION 34. Fuel Tank 1 7.5 7.5 EFB STATION 35. EFB Shredder Machine 1 75 75
36. EFB Fiber Press 1 45 45
37. Hammer Mill Machine
38. Rotary Dryer 1 75 75
39. Baler Machine 1 60 60
DOMESTIC USAGE AND WATER TREATMENT PLANT 40. Office, Laboratory,
Storage Room, Workshop, POME Treatment Plant, Raw Water Treatment Plant
1 200 150
TOTAL POWER 1312.1
3.9.1.2 Power Generation
Steam turbine is using steam from boiler to generate electricity. The exhaust steam from steam turbine will store in backpressure vessel for processing. Before running the boiler, diesel generator is used to supply electricity for palm oil mill. The amount of power generated for the designed mill is shown in Table X.
Table X: Power Generation. Steam Turbine
Total Power Consumption = 1312.1 kWh Output Power of Steam Turbine = 1500 kWh
Actual Output Power of Steam Turbine = 1500 kWh X 90% = 1350 kWh Steam Required for Steam Turbine = 25 kg steam/kWh
Total Steam Required = 25 kg steam/kWh X 1500 kWh = 37,500 kg Steam
Exhaust Steam for Processing = 37,500 kg Steam X 90% = 33,750 kg Steam
Diesel Engine Set
Output Power per Engine Set = 450 kW Total Diesel Engine Set Required = 3 3.9.1.3 Boiler Selection
Steam Boiler is any closed vessel in which for any purpose steam is generated under pressure and include any economizer used to heat water being feed to the boiler and any super
heater used for heating steam and any pipes and fitting connected there to. Table X shows the calculation of the required boiler plant for the designed mill.
Table X: Steam Boiler Selection. Data
Mill Throughput = 30 ton FFB/hour Raw Water Temperature = 27ºC
Boiler Feed Water = 80ºC Boiler Safe Working Efficiency = 85%
Steam Required for Turbine = 37,500 kg Steam/hour Boiler Steam Capacity Capabilities = 45 ton of Steam/hour X 0.85
= 38.25 ton of Steam/ Hour
From the above calculation, the mill needs 37.5 ton of Steam/hour for steam turbine to generate electricity. But in term of long term planning, the mill was installed boiler with capacity of 45 tons steam/ hour. The working pressure of boiler is 22 bar with processing temperature of 260ºC.
3.9.1.4 Fuel Availability
For this mill, EFB will not be used as boiler fuel as it will further processed to become value added by product. The fuel source for boiler is mainly for mesocarp fiber and palm shell. The calorific value of mesocarp fiber and palm shell is 19,000 kJ/kg and 18,836 kJ/kg respectively. The amount of boiler fuel required is calculated as shown in Table X.
Table X: Boiler Fuel. Data
Amount of Palm Shell = 30 ton FFB/hour X 5.2% = 1,560 kg shell/hour Calorie Value of Palm Shell = 19,000 kJ/kg
Amount of Mesocarp Fiber = 30 ton FFB/hour X 19.25% = 5,775 kg fiber/hour Calorie Value of Mesocarp Fiber = 18,836 kJ/kg
Heat Required to Heat 1 kg of Steam at 22 bar in Boiler From Steam Table
At 22 bar, hf = 930.562 kJ/kg & hfg = 1869.4 kJ/kg
h = hf + xhfg
h = 930.562 kJ/kg + [0.9 X 1869.4 kJ/kg] h = 2613.022 kJ/kg
Heat Already Present in Water Q = cp X T
Q = 4.187 kJ/kg. ºC X 80ºC Q= 334.96 kJ/kg
Heat Required to Generate 1 kg of Steam h = 2613.022 kJ/kg - 334.96 kJ/kg h = 2278.062 kJ/kg
Steam Required For Boiler = 38.25 ton of Steam/hour
Heat Required to Generate Steam = 38,250 kg of Steam/hour X 2278.062 kJ/kg.kg Steam = 8.71 X 107 kJ/kg.hour
Amount of Fuel Required to Generate Steam Palm Shell
Let assume heating efficiency of 70%
h = 1,560 kg shell/hour X 19,000 kJ/kg X 0.7 h = 2.075 X 107 kJ/kg.hour
Mesocarp Fiber
Let assume heating efficiency of 70%
h = 5,775 kg shell/hour X 18,836 kJ/kg X 0.7 h = 1.08 X 108 kJ/kg.hour
Total Heat Generated
h = 2.075 X 107 kJ/kg.hour + 1.08 X 107 kJ/kg.hour = 1.288 X 108 kJ/kg.hour
From the above calculation, burning of palm shell and mesocarp fiber is enough to generate sufficient steam for processing of CPO.
3.9.1.5 Summary of Power Balance
Table X: Overall Power Balance.
Power Generation Power Consumption Power Loss 1350 kWh 1312.1 kWh 37.9 kWH Steam Generated Remaining Steam Steam Loss
