I. STEAM POWER
I.a. For 20 TON FFB:
- Steam required for processing : 12348 kg/hr.
- Steam available : 11324 kg/hr.
- Steam balance : 1024 kg/hr.
i.e. Fuel (Fibre + Shell) are not enough to generate the required steam for this reason, thus supplementary fuel (for example empty bunch) has to be used. I.b. For 25 TON FFB:
- Steam required for processing : 14017 kg/hr.
- Steam required : 14182 kg/hr
- Steam balance : + 165 kg/hr.
i.e. surplus of fuel. I.c. For 30 TON FFB:
- Steam required for processing : 15456 kg/hr.
- Steam available : 17043 kg/hr. -
Steam balance : +1587 kg/hr.
i.e. surplus of fuel.
II. ELECTRIC POWER
II.a. For 20 TON FFB:
- Electric power required for processing : 564 kW - Electric power available for processing : 566 kW - Power balance is : + 2 kW
That means that steam production is sufficient to generate the required power.
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II.b. For 25 TON FFB:
- Electric power required for processing : 564 kW - Electric power available for processing : 709 kW - Power balance is : +145 kW
That means that steam production is sufficient to generate the required power (surplus).
II.c. For 30 TON FFB:
- Electric power required for processing : 620 kW - Electric power available for processing : 844 kW - Power balance is : + 224 kW
That means that steam production is sufficient to generate the required power (surplus).
SUMMARY
A. Mill capacity 20 TON FFB/hr:
1. To obtain sufficient steam/power for processing, shredded and dried empty bunches could be utilized as fuel.
2. Boiler capacity: 15 T/hr
3. Turbo alternator output: 650-700 kW (in order to cover additional power requirement for empty bunch treatment plant).
B. Mill capacity 25 TON FFB/hr:
1. Steam and power can be sufficiently generated from fuel available. 2. Boiler capacity: 18 T/hr
3. Turbo Alternator output: 600-700 kW (in order to fully utilize the steam available).
C. Mill capacity 30 TON FFB/hr:
1. Steam and power can be sufficiently generated from fuel available. 2. Boiler capacity: 18 T/hr
3. Turbo Alternator output: 700-950 kW (in order to fully utilize the steam available).
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NOTE 1:
The above figures are merely shown as an example and should not be taken literally when calculating the requirements for a particular plant/factory.
Each factory has its own specific needs and these should be taken into consideration when calculating its requirements.
NOTE 2 :
From the working results of palm oil mills which utilise empty bunches mixed with fibre and shell as fuel, it has been shown that as a consequence of burning the bunches a large part of the other wise available potassium salts are wasted.
Regular boiler ash analysis for K20, have given percentages of 4, 9, to even 12% thus, not all potassium salts are wasted.
It must be noted that the figures of low K20 content concerned boilers on full load and the high K20 figures concerned boilers on low load. Further more, the K20 content of fly-ash from the flues and chimneys in its turn is higher then the K20 content of ashes from the furnace grate, for instance:
In HCl soluble K20
grate ash flue ash 1st sample 12.04% 16.38 %
2nd sample 7.06% 12.75 %
3rd sample 9.28% 14.92 %
Thus a part of the potassium salts is carried along with the smoke gasses in some form and later on, when these gasses cool down, it will crystallize as fine dust and deposit with soot and other particles on various places in the smoke gas flues.
Investigation in to the reasons for (violent) corrosion have comprised a qualitative chemical analysis of the acid liquid between the "iron blisters" and corroded parts.
The tests showed that the existence of Mg - K - NH4 - iron Cl and SO4
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Unless the burning of empty bunches in the boiler furnace is absolutely necessary in order to maintain a positive fuel - steam – power balance, it is therefore not recommended.
34.8 ELECTRICITY
34.8.01 Since a palm oil mill utilizes the expelled fibre, shells etc. for fuelling its boilers and generating steam, it is obvious that it is advantageous to generate electricity for normal processing by steam driven alternators.
34.8.02 In order to be able to start-up the boilers and the process, there has to be electricity available before sufficient steam is raised to operate the steam driven equipment and this is commonly achieved by generating electricity with diesel driven alternators.
34.8.03 In a well designed and correctly operated palm oil mill these diesel driven units should never be used to operate the main process lines and in fact the capacity of these units should be chosen such that there is sufficient power generated to allow for a correct start-up (and stopping) of the boilers and auxiliary equipment, but definitely insufficient to "run" the factory.
34.8.04 Steam turbines have now largely replaced all other types of steam drive units for alternators in palm oil mills.
The steam turbine type most commonly used is designed to operate on the full steam pressure as generated by the boiler(s) and has a "back pressure" (or exhaust steam pressure) which is sufficiently high to be utilized for the sterilization process and the various heating applications in the oil mill.
34.8.05 The introduction of the water tube type steam boiler with super heated steam etc. has aided the introduction of a fairly large assortment of steam turbines into the industry, each with their own particular characteristics, their good point sand their "failings".
34.8.06 As for many other (specific) machinery in the mill, it would be outside the scope of this book to enter into too much detail for particular machines as it is far better to extract specific information from the manufacturers instruction manuals and hand books.
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starting and stopping procedures to be observed and correct load balancing when these machines are operating.
Ideally this load balancing should be automatic and not manually controlled, so that actual kW loads and power factors etc. are equally shared out on the system, if more then one unit is operating in parallel with others.
34.8.08 Good and continuous supervision is the key word here and can save considerable amounts of money, by ensuring that correct operating procedures are followed and that diesel driven generator usage is restricted to the start - stop periods of the mill only.
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