Steriliser Type 1

Engineering & Process Handbook For Palm Oil Mill Sterilization

TOPIC 2 Sterilization

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Introduction Sterilization is the most important process in the production line. Steam is used as the medium to transfer the necessary heat required to raise the temperature of the oil palm’s Fresh Fruit Bunch (FFB). It is used because it is cheap and readily available from the operation of the boilers and steam turbo-alternators. Moreover, it is convenient and suitable for this purpose.

The FFB delivered and received at Palm Oil Mill must be sterilized as soon as possible to avoid the rise in Free Fatty Acid (FFA) during prolonged storage. It is of paramount impAortance that sterilization is carried out properly and effectively. Otherwise, it will affect the recovery of oil and kernel. The present method of sterilization of FFB is a batch process. With well-thought of design and planning of sterilizer layout, a continuous co ntinuous operation to supply sterilized FFB into the production line to sustain the designed Mill throughput can be easily achieved. With poor design of layout, any interruption in the supply of sterilized FFB will result in a disruption of downstream activities which lead to, not only reduction of throughput but also the loss of product. The main objectives of sterilization of FFB a re:a. Inactivation of Oil-splitting Enzymes Lipolytic enzymes responsible for the oil- splitting action 0 in FFB can be destroyed by heart treatment. A minimum temperature of 55 c is sufficient to render these enzymes inactive. Enzymes not inactivated will degrade palm oil by promoting the rise in Free Fatty Acids (FFA).

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b.

Loosening of Fruitlets From The Bunch Sterilization loosens the fruitlets in the bunch and facilitates their removal from the bunch during the stripping/threshing process.

c.

Conditioning the Mesocarp For Good Oil Recovery. During the process of sterilization, the mesocarp is softened. During digestion and pressing processes p rocesses the mesocarp will be separated from the nut n ut which is further polished p olished in the depericarper drum.

d.

Nut Conditioning For Better Cracking In order to achieve good nut cracking efficiency in the Nut Crackers or Ripple mills, the nuts must be dried to a given temperature for a given time. Normally, sterilization at a pressure of over 40 psig for 90 minutes or more will be sufficient to ensure good stripping of fruitlets and good nut cracking efficiency.

The main machinery in sterilization process is Sterilizer, and it is categorized as unfired pressure vessels. Sterilizer and its related related equipments will be further described in this topic.

Types of Sterilizer Currently there are six (6) types of sterilizer available in t he palm oil industry such as follows: a. Horizontal Sterilizer b. Vertical Sterilizer Oblique Sterilizer c. Tilting Sterilizer d. Ball Tipper (Spherical) Sterilizer e. f. Continuous Sterilizer

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The most common type of o f sterilizer used in the palm oil industry is Horizontal Sterilizer. a. Horizontal

Sterilizer – Type 1 With the increased milling capacity in modern palm oil mills, horizontal and larger size sterilizers are now commonly used. These are cylindrical steel tanks complete with one (1) or two (2) doors depending on the Sterilizer Station layout configuration. Their length and diameter depend on the cage size and mill throughput. The evolution of the cage sizes and sterilizer diameters are shown in Figure 1 (a) & (b).

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According to their length the vessels are mounted on two or more stools. The stool nearest to the door is fitted rigidly. The others rest on rollers in order to allow for the free expansion and contraction to which the shell is subjected by the ever changing temperatures within. The horizontal cylindrical steel tank shell is mounted on several supports or saddles. The number of supports required is dependent on the total length of sterilizer tank shell. Horizontal Sterilizers offer a wide variability in effective capacity: from two (2) FFB cages, each holding 1.5tons of FFB (i.e 3 tons of FFB per charge), to nine (9) FFB cages, each holding 2.5tons of FFB (i.e 22.5 tons of FFB per charge), and as high as four (4) FFB cages, each holding 16tons of FFB (i.e 64 tons of FFB per charge). They are designed as cylindrical, electrically welded steel pressure vessels. Their diameter is either 1700mm or 2100mm or 2900mm, depending on type of fruit cage used (for 1.5 tons or 2.5tons or 16tons). The length of the vessel is adapted to the number of cages it should hold.

2.5mt capacity

3.5mt capacity

12mt capacity

16mt capacity

Figure 1 (a): Evolution of FFB Cage size

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Figure 1 (b): Evolution of Horizontal Sterilizer diameter

The sterilizer door covers the full diameter of the vessel. It is perfectly balanced b y swivel arm fitted on top. Owing to this design the door can swing freely to the side of the sterilizer, allowing free access to the inside. As a general rule sterilizers have a door at one end only; they may, however, be fitted with doors at both ends. The doors are equipped with a safety device, which prevents opening before decompression and safety catches to prevent the doors from being blown-out after they have been moved to their open position. position. With one (1) door system, the support nearest the door is rigidly fixed whilst the rest are on rollers to allow for free movement caused by the expansion and contraction of the tank shell as a result of the the changing temperature. However, with the two (2) door system, the support at the centre is fixed whereas both sides si des of the remaining saddles are free to move.

Figure 2: Horizontal Sterilizer capacity of 2.5mt x 9 units FFB Cages x 4 units Sterilizer (One door system)

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Figure 3: Horizontal Sterilizer capacity of 16mt x 4 units FFB Cages x 4 units Sterilizer (Two door system).

Figure 4: Schematic view of Sterilization Station layout using Horizontal Sterilizer with Two Door System.

All Horizontal Sterilizers are normally provided with a pair of internal rail tracks to allow the FFB cages to be pushed in for sterilization. These are normally fabricated from square-bar or unequal angles. The complete sterilizer is insulated with rock wool insulation materials to prevent heat loss and for safety reasons. Most sterilizers in used are fitted with wear liners on the lower half of the tank shell to protect the corrosive actions of the condensate and erosion. Special care must be taken to ensure ‘gas-tightness’ of the welds joining these wear liners to the inner side of the sterilizer tank shell.

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Figure 5: Sterilizer insulated with rock wool material. Design Requirement – General The sterilizers and all its valves and fittings must be manufactured and tested in accordance with practice acceptable by the Factories and Machinery Department of Malaysia under the Ministry of Labor. They are normally designed and manufactured under the British Standard and ASME Code of Practice.

Figure 6: General arrangement of Horizontal Sterilizer with mountings and piping.

Figure 7: Horizontal Sterilizer with steam piping and safety valve.

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Two types of door shutting devices are being applied: the bayonet type and the umbrella type. Both types meet three important requirements: Absolute safety in everyday use. Perfect alignment to prevent leaking. Simple and rapid opening and shutting by unskilled labor.

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Figure 8: Pneumatically controlled valves for Horizontal Sterilizer

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Figure 10: Front view of Transfer Carriage

Figure 11: Side view of Transfer Carriage

Figure 9: Pneumatic valve program for operation of Horizontal Sterilizer

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a-1. Transfer Carriage (with or without Cage Push Out mechanism) mechanism) Transfer carriage system is for variety of different cage sizes used in a typical palm oil mill. For cage size from 3.5ton; 5ton to 7.5ton are typically twin cage or triple cage per transfer carriage movement. For cage size of 10ton; 15ton to 16ton could use single single cage or twin cage transfer carriage depending on the design of layout and proper calculation of time study.

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Figure 12: Twin Cage Transfer Carriage

A few different types of design of transfer carriage for c age push out: Tilting type transfer carriage (using two cylinders to jack up platform). Undertow type transfer carriage (using hydraulic motor to push out). Indexer type transfer carriage (using cylinder to pu sh cage out). Empty type transfer carriage (cage charging and discharging of using Indexer mounted before each transfer carriage) Transfer Carriage c/w Rotary Lock Hydraulic System is designed to provide a faster yet smoother cage transfer operation from one lane to another.

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Transfer carriage is positioned precisely without much adjustment adjustment as compare to latching cylinder used in earlier design. Rotary Lock c/w bearings and other accessories provided driven by compact Hi Performance High Torque Low Speed. Fully automatic locking and un-locking un -locking thus alignment of carriages. Manual / Automatic available with Proximity sensors provided for inter-locking. Actuators used: •Carriage traveling forward & reverse. • Actuators Cage discharge: either hydraulic motor or hydraulic cylinder. Carriage alignment & latching: Hydraulic driven Rotary Lock is preferred now to two horizontally mounted tie-rod cylinders provide locking & latching of carriage.

Figure 13: Transfer Carriage without Cage Push Out mechanism

Figure 14: Transfer Carriage with Cage Push Out mechanism a-2. Undertow System Undertow system is used for FFB Cage movement in Horizontal Sterilizer. Undertow system is designed to suit the robustness of use while maintaining cost effectiveness and to meet requirement of continuous production. Its component provides higher uptime, increases

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system efficiency and reduces power losses due to low internal leakage. Two types of Undertow System namely: Undertow Conveyor i. ii. Undertow Link Chain

Figure 15: Undertow Conveyor

Figure 16: Undertow Conveyor for Cage movement from Tipper

Hydraulic system used in this application required a hydraulic power unit (HPU) to drive the high torque low speed hydraulic motor that is directly attached to a sprocket of undertow conveyor chain mounted on a frame with tipping dogs to push the cage. The movement could be forward and reverse via the directional control valve. The system could be customized to suit the requirement: HPU: Electric motor sized up for maximum system operating pressure at 250 bar. Built-in over-load & over-torque protection adjustable safety relief valve incorporated within. HPU is normally located near the actuator. 

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Smooth and reliable spool movement. Excellent inching operation by precision machined spool notches. Variable speed control. Installed on top of HPU. Actuator: Actuator: Radial piston motor fitted with planetary reducer. Hydraulic motor is of latest generation of high-torque low speed drive, providing high starting and running torque minimizing internal leakage. Controls:

Figure 17: Undertow Link Chain for Cage movement from Transfer Carriage

Figure 18: Undertow System for Cage movement into Sterilizer a-3. Indexer System Indexer System is also used for FFB Cage movement in Horizontal Sterilizer. Indexer system as Cage material handling that eliminates the need and use of tractors, bulldozers, capstans and winches of for Horizontal Sterilizer with Double Doors in Sterilization Station. The system is for owner looking for a process controlled instead of human dependable in sterilization station. Typical Cage size used varies from 10ton; 15ton; 16ton to 20ton and Sterilizer Diameter of 2700mm and 3200mm.

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Figure 19: Indexer System for Cage movement

Indexer system is a total material handling solutions in sterilizer station. The latest generation is less maintenance, bumper-to- bumper cage movement for single cage and/or twin cage movement. The indexer system package provides options on various equipment for material handling of Fresh Fruit Bunches: Loading Ramp via FFB Conveyors to Feeding Point FFB Cage Feeding to Dry End Transfer Carriage Dry End Transfer Carriage to move in FFB Cages to Sterilizer Moving out SFB Cages from Sterilizer to Wet End Transfer Carriage Wet End Transfer Carriage to Cage Tipper, to SFB Hopper, via SFB Conveyor to Threshing Station Moving Empty Cage from Tipper to Feeding Point     

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Figure 20: Indexer System for Cage movement between Tipper and Horizontal Sterilizer

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Figure 21: 21: Indexer System for Cage movement movement via Cantilever Drawbridge Horizontal Sterilizer

from/ to

sterilizer station and then to threshing and press station. This leads to significant improvement in productivity and enhanced throughput.

Figure 23: Schematic view of Sterilization Station layout using CMC System.

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Indexer Mechanism

Figure 22: Indexer System for Horizontal Sterilizer’s door. a-4. Compact Modular Continuous (CMC) System CMC systems as Cage material handling for Horizontal Sterilizer with Single Door in Sterilizer Station for owner looking for an enhanced automated material handling and steam management process controlled in a smaller foot print area. Typical Cage size used is 10ton for a single door 20ton Sterilizer or 15ton for a 30ton Sterilizer, with diameter of 2700mm and 3200mm, respectively. The Modular design is suitable for a 20tph to 120tph mill.

CMC systems derived the cage movement from earlier generation of Indexer system. Indexer movement is based on twin cage. As the building footprint is small, thus this is compact, modular, continuous run material handling system for the sterilization process to perform synchronization and control of flow of FFB from loading ramp to

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Figure 24: CMC with Indexer System for Horizontal Sterilizer and Cantilever Drawbridge.

Figure 25: CMC with Indexer System for Horizontal Sterilizer’s door.

The CMC package provides with an enhanced technology on various mechanical; power transmission and automation equipment from Loading Ramp Station to Threshing Station to the following flow: Loading Ramp via various FFB Conveyors to Feeding Point. Feeding Point is utilizing FFB Hopper Hoppe r as storage buffer for Tipper. Moving out SFB Cages from Sterilizer to Tipper via Indexer. Tipper to SFB Hopper, via SFB Conveyor to Threshing Station. FFB Hopper to fill empty Cage Ca ge in Tipper. Moving in FFB Cages from Tipper to Sterilizer via Indexer.      

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Figure 26: CMC with Indexer System for Cage movement between Tipper and Horizontal Sterilizer. Some of important recognized benefits are: Improvement in working conditions and safety for operators as well as reducing manual handling of the cages. Ease of monitoring: Monitoring of movement of indexer is via automation system. Control Panel grouping are available via Integrated Indexing Systems or Simple Indexing Systems. Remote Console Panel controls different equipment to perform multiple functions as well as interlockAing. Ease of operation: Easy to operate using a single touch control on push buttons as well as Remote Consoles. Control: Auto/Manual/By-Pass -- Auto mode will move the hydraulic cylinder on indexer to forward and backward stroke until the cage moves forward by a distance of cage length. Manual operation would require operator to

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operate via push buttons on Remote Consoles. By-pass operation is for operator to operate via Local Panels nearby each grouping of equipment.

Figure 27: CMC System’s Control Panel via Integrated Indexing System. a-5. Compact Hydraulic Wire Rope Winch System Wire rope winch system is design for Horizontal Sterilizer, line pull for position in between sterilizer rail track line. Typically used for replacement of double drum capstan driven by electric motor gear-motor as well as for cage handling using winch design.

The main advantage of hydraulic driven winch is on the following: It comes with wire rope and hook; manual or solenoid control valve; starter panel for Hydraulic Power Unit (HPU), option of stainless steel (SUS) tubing or mild steel tubing. Hi-performance High Torque Low Speed radial piston motor specially designed for palm oil industry with option of free-wheeling. free-wheeling. Option of variable winch speed if choosing solenoid directional control valve. HPU is sized up for maximum line pull force with extra safety factor of 1.5 times. Width of Compact Winch Drum is standardized to less than one meter for all different sizes. Built-in over-load & over-torque protection adjustable pressure relief valve for preventing wire rope to snap. Full drum reversal at maximum line speed capability. For maintaining wire rope in winch drum when not in used.

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The following Winch Drum capacity is made available for pulling a train of cages of different capacity (3.5ton / 5ton / 7.5 ton / 10ton / 15ton). Wire rope used is of 6x36 IWRC from φ16mm; φ18mm; φ20mm to φ22mm. 3-ton line pull capacity for 40-ton 4/5-ton line pull capacity for 75 to 90 ton 7-ton line pull capacity for 120ton 10-ton line pull capacity for 150ton 12-ton line pull capacity for 180ton

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Hydraulic system used in this application required a hydraulic power unit (HPU) to drive a high volumetric and mechanical efficiency high torque low speed hydraulic motor that is directly attached to a mechanical winch drum. The drum outer surface machined with grooves for easy wire rope pay-in and out. The movement could be forward and reverse via a manual control valve installed on top of the winch structure or mounted at an elevated platform. Both Horizontal Wire Rope Winch and Vertical Capstan with Hydraulic Drive are available.

Figure 28. Hydraulic Power Unit and its connection to Winch Drum using Stainless Steel or Mild Steel Tubing

Figure 29. Side view of Hydraulic Driven Winch Drum

Figure 30. Front view of Hydraulic Driven Winch Drum complete complete with Wire Rope 15 | P a g e


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Steriliser Type 1

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