Press Release Body: The following paragraphs are included to give the buyer an idea of the scale and number of operations required to extract oil from oilseeds at a commercial level, and how they relate to small-scale operations. The main difference is that commercial mills refine the oil before offering it for sale as an edible product. It must be stressed that good quality unrefined oils produced by small-scale methods are in no way inferior to refined oils, and that they are, in many cases, preferred by the consumer as they retain the flavour of the oilseed. In oil mill the seeds are subjected to a number of processing steps prior to oil extraction. The oilseed is cleaned to remove trash, dirt, sand and metal pieces. The oilseed is then weighed for accurate control of oil and cake yield. The shell or seed coat is often removed from the oilseed kernel. This process is known as decortication and, as well as raising the oil content of the raw material entering the extraction machinery, it ensures a higher protein content in the oil-cake. Size reduction of the seed is sometimes followed by rolling to produce flakes which are then conditioned. during conditioning, The seed is heated and often treated with steam in order to rupture the oil-bearing cells and maximize the oil extraction efficiency. Oil-cake is passed two times through the expeller again to remove more oil. Small-scale oilseed processing Various small-scale techniques are available to enable people in rural areas to process their own oilseeds locally. Careful consideration is needed to select the system that will best suit the local circumstances. These circumstances include the scale of operation required, the availability of a power source, and a number of other factors. The general processing steps involved in oilseed extraction , but actual practice varies according to the nature of the seed. Decortication Some oilseeds have a hard outer shell which must be removed before processing. This process is called decortication. Palm kernel is an example of a seed that must be decorticated prior to processing. The extraction of oil from other oilseeds which can be processed without decorticating them first, such as sunflower, may be aided by removing a proportion of the hulls before processing.
Seed cleaning It is essential to winnow and sieve oilseeds, prior to expelling, to remove as much dirt, dust, sand and small stones as possible. The presence of sand results in high wear on critical components of expellers such as cages, wormshafts and cone. Using clean oilseed for expelling will greatly increase the time that the expeller can be used before replacement parts are needed. Size reduction Generally, small oilseeds (such as sesame or rapeseed) can be processed directly, while larger seeds (such as copra orother big size fruit need to be ground before processing. The most common type of powered mill used for small-scale operations is the hammer mill. Rolling Rolling a seed generally results in an improvement in oil extraction by increasing the surface area of the seed while at the same time retaining channels for the flow of oil. The flakes should be very fine and preferably thinner than 0.1 mm. Rolling before processing in a bridge press is said to increase oil yields by 10% for palm kernel, groundnut and sunflower. Conditioning Conditioning or \'cooking\' oilseeds involves heating the oilseed in the presence of water. The water may be that which is naturally present in the seed, or it may be added. The changes brought about by conditioning are complex but include the coalescence of the small droplets of oil, present in the seed, into drops large enough to flow easily from the seed. In addition, higher processing temperatures improve oil flow by reducing the viscosity of the oil. Oilseeds are nearly always conditioned before large-scale expelling. Small-scale expellers minimize the need for pre-treatment by using a relatively fast wormshaft speed which shears the oilseed as it passes through the expeller and produces frictional heating within the expeller chamber cage set. This assists oil expulsion by raising the temperature of the oilseed. However, even when using a small-scale expeller, oil extraction will be assisted by heating and/or steaming the oilseed before expelling. Heat treatment is essential for some seeds with a low fibre content such as groundnuts; they must be heated and moisturized before expelling or the machine will produce an oily paste instead of oil and cake.
Oil extraction without steam boiler This method involves the addition of a small quantity of water to the oilseed before the oil is extracted in the screw. Principle of operation Oilseed expellers produce oil and oil-cake from oilseed continuously,the expeller is driven either by an electric motor or by a diesel engine. At the heart of the machine is a powered wormshaft which rotates inside a closely fitting cage. The oilseed is fed continuously into the press through a hopper and is crushed as it is transported through the cage by the wormshaft. Pressure is exerted on the system by restricting the gap at the end of the cage through which the oil cake is discharged from the press. The expelled oil drains out of the cage through small gaps.The friction generated inside the expeller chamber will eventually result in the wearing down of the worms at the end, cage bars, cone rings, and cone. Replacement of these parts will be required at intervals depending on the type and amount of oilseed processed and the degree of dirt contaminating the seed. Rapid wear is a particular problem when expelling undecorticated, dirty sunflower seed or any oil seeds. The availability and cost of wearing parts are important considerations when setting up a small-scale expeller facility. General method of operation for expellers having an adjustable cone. Starting up the press 1. Before starting up the drive to the press, check that all the safety guards are in good order and the machine has been lubricated according to the manufacturer\'s instructions. Ensure the cone control is adjusted so oil-cake can be discharged from the press cake outlet very easily. 2. Start the expeller and check that the wormshaft is turning over correctly. Then begin feeding the oilseed very gradually by hand into the hopper. The screw press will not expell oil satisfactorily until the chamber box is hot. The operating temperature required varies according to the type of oilseed processed, but it is normally between 60 and 100°C. Some oilseeds (such as copra) have a fibre content which provides the friction needed to heat the chamber box. Softer oilseeds (such as groundnuts and sesame seed) first need to be heated and conditioned in order to reach a satisfactory operating temperature. When expelling the softer seeds, the time taken to reach the operating temperature can be reduced considerably by feeding the press cautiously by hand with crumbled oil-cake of the seed being processed. As the chamber box temperature increases seed should be mixed with the oil-cake in progressively increasing proportions so that finally only oilseed is being fed to the press. In some circumstances it is beneficial to use a mixture of oilseed and oil-cake all the time. 3. When the seed material has been discharging freely from the press cake outlet for a few minutes, the cone may be reduced gradually to increase the pressure within the press and improve the quality of the oil-cake and the oil flow from the chamber press . The optimum cake thickness for a small-scale expeller is usually about 1-2.5 mm. 4. The cone is adjusted by the wormshaft regulator at the feed end of the machine. Turning the handles clockwise moves the taper cone section of the wormshaft axially further into the taper bore of the conering, thus reducing the thickness of the cake. Turning the wormshaft regulator anti-clockwise withdraws the shaft and increases the cake thickness. 5. Until the chamber reaches the operating temperature, a large amount of sediment may be produced with the oil. To limit this, oilseed should be fed slowly to the press during the warming-up period. However, some oilseeds do not produce a large amount of sediment with the oil during the start-up period. In this case, the rate of feed may be increased more quickly until optimum operating conditions are reached. Once uniform operating conditions have been reached, the sediment can be gradually mixed in with the oilseed fed to the press. Normal operation of the press When uniform operating conditions have been reached, the objective should be to produce the best quality of oil-cake possible, consistent with the required throughput of the press. It is possible to process some oilseeds without needing to restrict the rate at which they are fed to the press. In other words, with the feed control slide on the hopper fully open, the press will continue to operate in a uniform and steady manner, drawing oilseed from the full hopper. When feeding from a full feed hopper, the flow characteristics of some materials through the press may be exceptionally good and result in a press capacity higher than required. If this condition occurs, the resulting residual oil in the cake tends to be high. A lower, more acceptable oil-in-cake result may usually be obtained by metering the seed to the press at a reduced rate. The importance of quality in small-scale processing Oil deterioration tends to lead to increased levels of FFA, poor colour, and flavour changes. Although poor quality oils can be purified or refined using large-scale equipment, this results in a loss of material. Also, since it is difficult to carry out at a small-scale all the refining stages that are possible in large-scale equipment, it is very important to ensure only high quality oil is produced. Steps to ensure this are enumerated below. . As far as possible, purchase good quality seed free from mould. . Store the seed under clean dry conditions. . Process the seed on a \'first in, first out\' basis, i.e. the oldest seed is processed first. . If the seed needs to be ground before the oil is extracted, only grind the amount required for each day\'s processing. The oil in ground seed tends to deteriorate rapidly and so ground seed should never be stored. . Clarify crude oil from the extraction process as soon as possible after production and store it in clean dry containers. The presence of solid matter in oils invariably leads to deterioration. . Bottles and containers used for the sale of oil should be both clean and dry. They should be kept as full as possible and sealed so as to limit contact with oxygen from the air.
Web Site: http://www.rajkumaragromachinery.com
Contact Details: RAJKUMAR AGRO ENGINEERS PVT. LTD. Supplier & Exporters of Mini Oil Mill Plants & Agricultural Equipment
Near Union Bank of India, Ghat Road, Nagpur - 440 018 (M.S.)