This is what to and a how to article for palm oil mill existing and aspiring palm oil mill management staff. This is a brief article and in future there will be other articles on specific topics for mill management.
This article is written because many managing staff have not been taught management and have been promoted to management positions due to experience.
This article is also for Palm oil mill owners and company senior management staff so that they understand what can be expected of a palm oil mill.
For detail explanation of the technical aspects the readers should refer to other sources of information or other articles.
A major characteristic of a palm oil mill is the very high rate of wear and tear of mill machinery. This is due to the nature of the fruits processed. The fruit fibres contain silicone and these causes wear. The fruits that arrive in the mill for processing also contain sand and dirt and these also contribute to the high wear rate.
What is a well operated mill?
A mill that can process fresh fruit bunches at the rated capacity and achieves a high extraction efficiency, with a below average industry production cost.
To achieve this following are required
A trained and experienced mill manager
Trained workers, workers who can take immediate actions if some machine is not performing as designed and adjust machines if the product loss is high.
A well designed mill
A system to monitor product loss and product quality
A system to communicate information to all in the mill, with regards to quality and efficiency
A system to maintenance the mill machinery
The manager responsible for the operations of the palm oil mill must first understand his major objectives. This will enable him to make his decisions and manage his time for the maximum profitability of the mill.
Suggested Objectives are
To process the crop at the rated capacity of the mill.
To achieve a high processing effiency ( More than 90%)
This is not always easy. Most of the mills are unable to process at the design capacity because of design defects. For example 60 tons per hour mill cannot process at 60 tons per hours for 20 hours per day if the maximun capacity of the mill is 60 tons/hr. The equipment wears out and the efficiency is not at its peak for all its operation life.
Every day when the mill starts in the morning it cannot immediately operate at its rated capacity. It normally takes about 30 minutes to 60 minutes for the mill to achieve its rated capacity. When the mill is shut down this process is reversed and all the conveyors, elevators and other equipment have to be emptied before all equipment is stopped.
The average throughput for the day will be less than 60 tons per hour and normally is about 90 % of the rated capacity i.e. 54 tons per hour. Therefore 60 tons per hour mill should be able to process 54x 20 = 1080 tons per day or 27,000 tons per month, assume 25 operation days per month. A well organised and maintained 60 ton/hr mill should be able to process 300,000 tons of FFB per year.
Many owners demand more that this from a mill. This will result in a mill to be run for longer hours and also on Sundays. This normally results in the mill breaking down more often and the end result is a less efficient mill. The above capacities are based on the mill stopping for a period of two weeks every year for major maintenance work, like the internal cleaning and inspection of the boilers and inspection of the steam turbines.
In normal off peak month operations the mill also stops one day a week for maintenance and cleaning.
The palm oil mill process consists of a series of machines processing the palm fruit components. There are more than 25 machines in series. If each machine is 99 % efficient the total process efficiency will be 99 To Power of 25.
The total line efficiency will be 77 percent.
Example: 0.99 x 0.99 x0.99 x 0.99 …= 0.0.77.
To achieve the design throughput the individual machines in the mill should be designed to have a throughput of 120 % of the desired throughput. Many mills are not designed to do achieve this capacity.
As an example the steriliser station must have a capacity of 120%, so that the last machine can achieve a capacity of 100 %.
How to achieve throughput?
To achieve throughput if the mill is design correctly, the mill management can take a few actions. These include the following
The mill equipment has to be looked after well so that it does not break down. The machines must be cleaned on a regular basis and any parts that have worn to limits of their use must be replaced. It is advised to have a planned schedule to carry out work. Most mills stop one day a week to carry out maintenance. Failure to do this will result in an unreliable mill.
Procedures to start up and shut down the mill need to be documented and workers trained to carry these out.
The best way to operate the mill correctly is to employ experienced mill management staff who can guide the workers to take the correct actions when a problem arises.
Train staff in their jobs.
The mill supervisors cannot be every where in the mill at all times. To achieve the best through it is advisable to train the workers to work efficiently. This should be a continuous process and carried out by the mill manager or outside staff if required.
To Achieve High efficiency
By this we mean to extract the maximum amount of oil and kernel from the fruits delivered to the mill. The mill cannot increase the quantity of oil and kernel that is in the fruits, this is the job of the plantation.
The mill can reduce the oil loss in the process. The major oil loss in the palm oil process occurs in the Fibre, Sludge and Steriliser condensate. ((90 % of all oil losses)
Oil Loss in press fibre.
This is minimised by operating the screw press at the correct pressure with the screws in good condition. The fruits must also be pre-treated well in the digesters. The pre-treating or mashing of fruits in the digester depends on how well the fruits are sterilised.
Therefore oil loss in the press fibre depends on, correct sterilisation, correct digestion and correct pressing. All these processes must be monitored to achieve a low oil loss in the press fibre.
Oil Loss in Sludge.
Oil loss is the result of poor separation process in the clarification station. To achieve a good separation the clarification tank must be operated correctly.
This is achieved by setting the skimmer in the clarification at the correct height (100mm to 150 mm) and by maintaining an oil water ratio of 30 % to 38 %. The dilution should be monitored at the crude oil tank by the use of a hand centrifuge on an hourly basis by the operators themselves.
Experienced workers can adjust the water by monitoring the number of turns of the water valve to achieve correct dilution, depending on the number of presses in operation.
The correct number of sludge centrifuges must be in operation. The nozzles must not be worn above the allowed limits. To achieve a good efficiency the sludge centrifuges must be maintained well.
The most common way to loose oil in sludge is to discharge un treated sludge into the drain. This normally happens when there is insufficient sludge centrifuge capacity.
The oil loss occurs due to a longer than necessary steriliser cycle or due to over ripe fruit. When the fruit is over ripe, the mill should shorten the steriliser cycle.
Kernel Loss occurs in the pneumatic kernel separators and the hydro cyclone. And press fibre.
For a mill to have low kernel loss the following must be attended to
Low nut breakage in the press; - Do not press at a very high pressure
Kernel loss in press fibre- Due kernel breakage in the screw press because of too high a press pressure.
A high cracking efficiency ensures lower kernel loss as there are less un-cracked nuts.
Monitoring of mill efficiency.
The function of process control is to help management to achieve a high efficiency.
This is achieved by taking the required samples and analysing them and reporting the results to management for action.
The following samples should be taken and analysed
Oil loss in condensate
Oil loss in press-cake
Oil loss in sludge
Oil loss in final effluent
Oil Loss in steriliser condensate.
Percentage cracked nuts in press-cake fibre
Kernel loss in press fibre
Kernel loss in pneumatic separators
Kernel Loss in Hydro cyclone
Proper separation of oil in sludge the sludge centrifuges.
To monitor oil quality, the following samples are required.
Free Fatty acid content of production oil
Dirt content in production oil
Moisture content in production oil
To monitor kernel quality, the following samples are required.
Moisture content of production kernel
Dirt content of production kernel.
Staff Requirements for a palm oil mill
Electrical Charge man
The total number of workers in a modern 60 tons per hour palm oil mill should be about 130 workers for three shift operations.
The end of this brief article
By the POMILL team