Effect of different sterilization methods on the extracted oil from oil palm fruit in plam oil mill

Sterilization is one of the key processes in any palm oil mill plant. Fresh fruit bunches (FFB) are cooked using steam as the heating medium. The sterilization process uses a lot of steam, consuming about thirty (30%) to sixty (60%) percent of the total process steam, depending on the type of sterilizer technology used. The type of sterilizer technology utilised has a major bearing on the steam consumption and pressure (temperature) of the sterilization process.

The sterilization method utilised also affects process performance and quality of palm oil. The good bleachability of palm oil necessitates a proper air-release prior to sterilization, shortest possible sterilizing time and lowest possible process temperature. Conventionally, in a palm oil mill plant the sterilization process is carried out in cylindrical pressure vessels, lying in horizontal or vertical position, and filled with steam under pressure as a batch process. Of late, sterilization process is also being carried out as a continuous process in a heating cabin filled with steam at atmospheric pressure. Process steam consumption for the sterilization process varies between 110 kg to 400 kg per tonne FFB depending on the type of sterilizer technology utilised. The following discussion on the different types of sterilizer is centred on its relevance to steam and power consumption and thus, overall energy efficiency of the palm oil extraction process.

Horizontal Sterilizer

Horizontal-sterilizer is the most commonly used sterilizer in palm oil mill palnt.When disposed in a horizontal position, the cylindrical vessel sterilizer has fairly good disposition because the oil palm fresh fruit bunches placed in cages with a low stacking height are more uniformly spread out in this position across the length of the elongated vessel, as opposed to a vertical sterilizer. Thus, when pressurized steam is injected into the interior of the horizontally positioned cylindrical vessel, the steam can reach out to different directions and corners of the contents within the cages thereby helping treatment of the fruit bunches. Due to the low stacking height of the fruit bunches in the cages, condensate drains out freely from the fruit bunch stack facilitating heat penetration. The low stacking height also limits fruit bunch compression that facilitates low oil loss from the fruits during sterilisation.

Horizontal sterilizer in palm oil mill

Vertical sterilizers

Vertical sterilizers is another type palm fruit sterilizers which can save space.However, due to considerable stacking height and resulting fruit bunch compression in the vertical vessel, air removal and condensate drainage from the fruit bunch stack is restricted and this impedes heat penetration. The design requires higher steam pressure with multiple-peak cycles and a longer sterilization time for effective heat treatment of the fruit bunches resulting in higher steam consumption.

The vertical sterilizers use steam at a temperature of 143 °C and with steam consumption between 305 and 355 kg / tonne FFB and a sterilization time of about 60 minutes in triple-peak cycles.

This method of sterilization involving high temperature and fruit bunch compression incurs high oil absorption into the empty fruit bunches and sterilizer condensate, affecting process efficiency. Thus, commonly where vertical sterilizers are employed, the empty fruit bunches are further processed to recover the oil absorbed in the stalks and fibres to increase the oil yield by shredding and followed by either pressing or solvent extraction – one that consumes considerable extra power. Significantly, the oil recovered from the empty fruit bunch pressed liquor are prone to contaminants like potassium, chlorine and phosphatides that are detrimental to the quality of production oil, and imposes difficulties at the refining stage.

Vertical sterilizer in palm oil mill

Henan Doing Coampany is a professional manufacturer of palm oil processing plant. Now we developed new technology which allow for easy, quick and complete air removal from the conventional horizontal sterilizers. The new technology together with the inherent freely draining condensate enable the horizontal sterilizer to effect the most energy efficient sterilization process in palm oil mills. The new sterilization method cam ensure steam consumption as low as 110 to 130 kg per tonne FFB and a sterilization time of about 40 minutes to achieve effective sterilization.More information about palm fruit sterilization machine, you can contact us , our engineers will introduce more details to you.